classhomeworkwebpage.weebly.comclasshomeworkwebpage.weebly.com/uploads/1/3/6/8/13685067/... · Web viewMechanical Advantage The of an inclined plane is:MA = output force (Distance

Science 8Mechanical

SystemsStudent Notes Booklet

Name: ________________________________

Class: _______________

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Simples Machines – Inclined PlanesQuick Review:

• The ____________ for _________________ are _________________________!

▫ We have used spring scales to measure this so far

The spring scales we have used measure 1N to 20N

• The force ____________ put into something is called the ________________ or _________________

• The force the machine does is called the ___________________ or the _____________________

Inclined Plane or Ramp

• An ______________________ makes it possible to lift heavy objects using a smaller force

• An ___________________________ is a slanted surface used to raise an object.

▫ A ramp is an inclined plane.

When an object is moved up an inclined plane, less effort is needed than if you were to lift it straight up, but, you must move the object over a greater distance.

• A _________________ is usually only useful for small inclines.

▫ The steeper the angle of the ramp, the harder it is to control the motion of an object

Mechanical Advantage

• The ___________________________ of an inclined plane is:MA = output force (Distance the load is going) input force (height the effort needs to be applied for)

Examples:Calculate the Mechanical Advantage of Each of the following inclined planes

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Height the effort needs to be applied for Input force

Distance that the load is going Output force

What does the mean?

• All inclined planes will give a mechanical advantage but which are the best?

• From our examples, it seems like the

▫ ones that have less HEIGHT require less force

▫ Ones that have more HEIGHT require more force

What if we used a pulley too?

• A _______________ will ___________________ the amount of force needed to move an object up an inclined plane

Friction

• We have NOT considered _______________________

• ___________________ occurs whenever two surfaces rub against one another

▫ Friction is the force that goes against (opposes) motion

• A ____________________ creates ___________________ than a smooth surface

• THIS MEANS: Extra force is needed to overcome friction when you move an object

▫ This can affect our mechanical advantage.

• What happens when two object rub against one another?

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20 cm100 cm

10 cm 200 cm

75 cm300 cm

▫ It creates HEAT!

Examples of Friction

• When a driver wants to stop a vehicle, friction is created where?

• When you are writing notes in science class, friction is created where?

LEVERS

Way Back When

• The earliest machines were very simple devices.

– _________________ to pry rocks out of the ground

– _________________ to help raise rocks as walls were built

• The first machines all had something in common…

– THEY ALL DEPENDED ON PEOPLE OR ANIMALS FOR THEIR SOURCE OF ENERGY

Roman Aqueducts

• Thousands of years ago, Roman engineers developed a

mechanical system for transporting water for many

kilometers.

– They were made of:

• Pumps

• Ramps

• Distribution systems

Meeting the same needs in different ways

• Water is a ______________• Before we had taps with pumps like we do now, engineers used ___________________

to help move water through pipes.

– A __________________ was used

• Had a series of buckets attached to long ropes which was draped over a

wheel

• Animals such as donkeys turned the wheel, raising the buckets of water

Archimedes Does Better

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• _________________ invented a screw to help move water.

– More efficient ways were always looked for

• An ___________________ can move large amounts of water

Simple Machines

• A ___________________is a tool or device made up of one simple machine

– Lever

– Inclined Plane

– Wedge

– Screw

– Pulley

– Wheel and Axle

Lever

• A ____________________ is a rigid bar or plank that can rotate around a fixed point

called a

_________________.

• _________________ are used to reduce the force needed to carry out tasks like:

– Pulling nails

– Opening bottles

– Hitting a baseball

– Cutting Paper

• With a lever you can move a larger load than you could without using it.

3 Kinds Of Levers

• 1. First class lever

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• 2. Second class lever

• 3. Third class lever

First Class Levers

• A ___________ has the _____________ ______________ the ____________ and the

__________

Second Class Lever

• A ____________________ has the ___________ ___________ the __________ and

the _________________

Third Class Lever

• A _____________ has the _____________ ___________ the ______________ and the

______________.

• We build machines for ____________ reasons:

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– 1. To go faster or further

» Distance/Speed Ratio

– 2. To make ourselves seem stronger or increase the amount of force we can

apply

» Mechanical advantage


• A person on their own would never be able to lift a car.

– A lever could make this possible!!!!

– A scientific explanation for this is the lever provided

__________________________• The ____________________ of a machine is the amount by which a machine can

multiply a force

– The force applied to the machine is called the _________________– The force the machine applies to the object is called the _________________

• FORCES ARE MEASURED IN NEWTONS!

Mechanical Advantage (MA) = Output Force

Input Force

• If the Mechanical Advantage is:

– __________________ The amount of force you are putting in is MORE than

the force you are getting out.

– ___________________ The amount of force you are putting in is THE SAME AS the force you are getting out.

– ___________________ The amount of force you are putting in is LESS than

the force you are getting out.

Example:

If we had a first class lever that takes 45 N to lift a 45 N weight.

MA =

This means, the amount of force you are putting in is the EXACT same as the force you are

getting out.

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If we had a first class lever that takes 45 N to lift a 180 N weight

MA =

This means, the amount of force you are putting in is less than the force you are getting out.

This is a good Mechanical Advantage.

If we had a first class lever that takes 180 N to lift a 45 N weight

MA =

This means, the amount of force you are putting in is MORE than the force you are getting out.

This is a bad mechanical advantage.

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FIRST CLASS LEVERS LAB

Spring Scales- Spring scales are designed to be used upright and to measure lifting forces.

STATION 1: PRACTICE WITH SPRING SCALES1. How much force does it take to lift a 200g mass?

2. How much force does it take to life a 500 g mass?

3. How much does a GREEN (5N) spring scale weigh?

STATION 2: LEVER TERMINOLOGY

1. The FULCRUM is: _________________________________________________

2. The LOAD FORCE is: ______________________________________________

3. The EFFORT FORCE is: ____________________________________________

4. The LOAD ARM is the distance between the ________________________ and the __________________________________

5. The EFFORT ARM (sometimes called the FORCE ARM) is the distance between the __________________________ and the _____________________________.

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Load Effort Force

Fulcrum

Load Arm Force/Effort Arm

STATION 3: FULCRUM IN THE MIDDLEUse a meter stick, large weight, 5N spring scale and the fulcrum supplied:

1. Set up the fulcrum on the meter stick at 50cm.2. Figure out the weight of the large weight using the spring scale.3. Place the large weight on the zero end of the meter stick from the string provided.4. Predict how many Newton’s of force you will need from the spring scale to balance out

the lever.5. Measure the actual force needed to balance out the lever using the spring scale.6. Record findings on the chart below

The mass of the large weight is: ___________________________________

Fulcrum Position (cm) Predicted force from spring scale (N)

Actual force from spring scale (N)

50 cm

STATION 4: FULCRUM AT 30 CMUse a meter stick, large weight, 5N spring scale and the fulcrum supplied:

1. Set up the fulcrum on the meter stick at 30cm.2. Figure out the weight of the large weight using the spring scale.3. Place the large weight on the zero end of the meter stick by the string provided4. Predict how many Newton’s of force you will need from the spring scale to balance out

the lever.5. Measure the actual force needed to balance out the lever using the spring scale.6. Record findings on the chart below.

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You can get one of two different advantages when using a lever depending on how it is set up. The first advantage is called the FORCE ADVANTAGE or MECHANICAL ADVANTAGE. Mechanical advantage occurs when the effort force (input force) is multiplied therefore less force is needed to move an object. The force arm is longer than the load arm.




30 cm

Answer the following questions about station 3, and 4

1. Experiment to find the best way to lift a heavy load with the least effort possible. Describe or draw your findings.

2. In station 4, the EFFORT ARM is ________________________ (longer or shorter) than the LOAD ARM.

a. This will give us what kind of advantage?

STATION 5: FULCRUM AT 75 CMUse a meter stick, large weight, 20N spring scale and the fulcrum supplied:

1. Set up the fulcrum on the meter stick at 75cm.2. Figure out the weight of the large weight using the spring scale.3. Place the large weight on the zero end of the meter stick by the string provided4. Predict how many Newton’s of force you will need from the spring scale to balance out

the lever.5. Measure the actual force needed to balance out the lever using the spring scale.6. Record findings on the chart below.




75 cm

Answer the following questions about station 5:

1. The length of the load arm in this set up is _______________________(longer or shorter) than the force arm

a. The type of advantage you would get is: _________________________________

STATION 6: DIAGRAM IT!Look at the pictures of class one levers and label the following:

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The other advantage is called SPEED OR DISTANCE ADVANTAGE. When the lever is set up in this manor more force is needed but the object moves faster or covers a larger distance. The load arm is longer than the force arm.

a) Fulcrumb) Effort Forcec) Loadd) Load Arme) Effort/Force Arm

Also, tell me if these would be a mechanical advantage or a speed/distance advantage.

STATION 7: CALCULATE IT!Calculate the mechanical advantage of each of the following and what it means.

If a first class lever had a load of 50N and an effort of 200N.

If a first class lever had a load 500N and an effort of 250N.

If a first class lever had a load of 60N and an effort of 60N.

If your friend is sitting on your cell phone (he weighs 800N) and you want him off, you have a first class lever with a mechanical advantage of 6, how much effort force would you have to use to free your cell phone?

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SECOND CLASS LEVERS

REMEMBER:

- In a class 2 lever, the LOAD is between the FULCRUM and the EFFORT FORCE- The LOAD ARM is between the fulcrum and the load- The EFFORT/FORCE ARM is between the fulcrum and the effort force- If the EFFORT/FORCE ARM is longer than the LOAD ARM, it is a mechanical

advantage- If the LOAD ARM is longer than the EFFORT/FORCE ARM, it is a speed/distance

advantage

A. DRAW THE LOAD ARM AND THE EFFORT ARM

Since the force/effort arm is longer than the load arm, we have a mechanical advantage!

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B. SKETCH A DIAGRAM OF THE FOLLOWING PICTURES. INCLUDE:a. Effort forceb. Loadc. Fulcrumd. Effort/Force arme. Load arm

THIRD CLASS LEVERS

REMEMBER:

- In a class 3 lever, the EFFORT FORCE is between the FULCRUM and the LOAD- The LOAD ARM is between the fulcrum and the load- The EFFORT/FORCE ARM is between the fulcrum and the effort force- If the EFFORT/FORCE ARM is longer than the LOAD ARM, it is a mechanical

advantage- If the LOAD ARM is longer than the EFFORT/FORCE ARM, it is a speed/distance

advantage

A. DRAW THE LOAD ARM AND THE EFFORT ARM

Since the force/effort arm is shorter than the load arm, we have a speed/distance advantage!

B. SKETCH A DIAGRAM OF THE FOLLOWING PICTURES. INCLUDE:

a. Effort force

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b. Loadc. Fulcrumd. Effort/Force arme. Load arm

Second and Third Class Levers Lab

Second Class Levers:

1. Set up a class 2 lever using a weight, string, a weigh scale, and a meter stick.2. Measure the force needed to lift the meter stick to level.3. Was this force more or less than just lifting the weight with the weigh scale?

Predicted force needed Actual force needed Advantage?

Third Class Levers:

1. Set up a class 3 lever using a weight, string, a weigh scale, and a meter stick.2. Measure the force needed to lift the meter stick to level.3. Was this force more or less than just lifting the weight with the weigh scale?

Predicted force needed Actual force needed Advantage?

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Engineering Design Task:

You need to lift a large stack of books to the top shelf in the library using at least one lever.

Draw three different possible solutions:

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Choose the best solution that you came up with. Why did you choose that solution?

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

PULLEY!

What Is a Pulley?

• A _______________________ consists of a rope or wire moving on a grooved wheel.

– The two sides of the pulley can be called the ‘effort/force arm’ and the ‘load arm’

– Pulley’s are used to change the direction of a load force by:• Raising a load• Lowering a load

Three Types of Pulleys

• 1. Fixed Pulley• 2. Moveable Pulley• 3. Combination Pulley

Fixed Pulley

• The ______________________ is set up in _____________ position usually to the top of a structure

• The fixed pulley allows objects to move but there is ____________________________________________________________

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100 N

1

2

– The output force will be the same as the input force so the mechanical advantage is always 1

Moveable Pulley

• A ________________ is attached to and moves with the load that is being lifted

• Moveable pulleys allow you to move an object with ____________________ so the mechanical advantage is ________________________

Combination Pulley

• The _______________ that are added to a ___________________, the more ropes that are required to lift a load.

– A combination pulley has more than 1 wheel• This makes the mechanical advantage increase

Calculating Mechanical Advantage of a Combination Pulley

• To calculate the mechanical advantage of a compound pulley:– You count the number of ropes connecting the pulley’s together

EXCEPT the one your will be pulling on…EXAMPLES:

1. What is the mechanical advantage of this pulley and what would the effort force be if the load is 100 N?

2. What is the mechanical advantage of this pulley and what would the effort force be if there was a load force of 300 N?

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200 N

3. What is the mechanical advantage of this pulley and what would the effort force be if there was a load force of 200 N?

The complex MachineThe complex world

Simple machines are great, but in our complex world we NEED machines with an effort other than people.

Today, we are almost completely dependent on machines.

What would happen to us if we could not use machines?!

Complex Machines

______________________ are devices that are made up of several simple machines that work together.

A ______________________ is a group of parts that work together to perform a function.

Example

A __________________ is a _________________ for moving a person around.

A _________________ is something within a system that have just one function. (subsystems work together to help the device accomplish what it was built to do)

BIKES

___________________ – Moving people around

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300 N

___________________ – Braking, Steering

Your turn

THE PENCIL SHARPENER

What is the function of the device?

How many subsystems can you identify in the device?

Do any of the subsystems contain a simple machine?

Systems the transfer forces

A ____________________ is the part that transfers your energy from one part to another.

They transfer small amounts of energy

EXAMPLES:

Chain on a bike

Belts in car engines

A __________________ transfers energy from engines to the wheels.

They transfer large forces

Gears

___________________ consist of a pair of wheels that have teeth that interlink.

When they rotate, one gearwheel transfers the turning motion and force to the other.

The _____________ the _______________, the more slowly it turns but it has a ____________________________

The ______________________ the ______________________, the more quickly it turns

How gears work

Almost every device that uses spinning parts has gears

__________________ control the transfer of energy in the system

In a bike the gears allow the rider to change and control the speed of the wheels

Driving vs. Driven

The ___________________ is the gearwheel where the force is applied.

The ______________________ is the gearwheel that moves as a result of the other gearwheels moving.

How gears affect speed

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If the _______________________ is larger than the ______________________, the turning speed in the system increases.

The larger gear will turn around once and the smaller gear will turn around more than that.

________________ that increase the speed are called ______________________________

EXAMPLE: Egg beater

______________________ decrease the turning speed in a device.

The driving gear is smaller than the driven gear

_______________________ have two gears of the same size working together.

Summary

_________________________ – large to small gears

_________________________ – small to large gears

___________________________ – same size of gears

Wheel and Axle, Screw, Wedge

Wheel and Axle

• A _____________________________ is a combination of 2 wheels of different diameter

that turn together.

• The largest wheel is the _____________________

• The smallest wheel is the ____________________

• Examples of this type of wheel and axle:

• 1. Motor

• 2. Ski lift

• 3. Bike

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• Because the ________________ is

longer than the ___________________

we get a

________________________________

• Examples of this type of wheel and axle

are:

• 1. Steering Wheel

• 2. Door Knob

• Because the _____________________

is longer than the

______________________, we get a

______________________________

Screw

• A ___________________ is an inclined plane wrapped around a cylinder

• A ___________________________ gives you a __________________________.

• The closer the threads, the more of a force advantage you get.

• A ___________________________ can be used to convert

____________________ motion into ___________________ (straight) motion.

• EXAMPLE: Archimedes screw

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Wedge

• A _______________________________ is a two sided inclined plane that goes into an

object.

• By pressing on the wide end of the wedge, you can exert a force on the narrow

end so it splits an object apart.

• Examples:

• 1. Knife blade

• 2. Axe

• 3. Door stop

SIMPLE MACHINES REVIEW□ A simple machine is a tool or device made up of one basic machine□ A simple machine needs no motor, only a person to do the work.□ A simple machine can give one of three advantages:

Change of direction Mechanical Advantage Speed/Distance Advantage

Simple Machine Name Advantage Type & Why does it get this advantage?

Examples

First Class Lever

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Effort Force

2 Inclined Planes

Load

Load

Load Effort Force

Fulcrum

Load Arm Force/Effort Arm

Second Class Lever

Third Class Lever

Fixed Pulley

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Moveable Pulley

Combination Pulley

Inclined Plane

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Wheel and Axle

Wheel and Axle

Screw

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Load

Load

2 Inclined Planes

Effort Force

Wedge

Simple Machines Quiz Date: _______________

Topic 2.1 – Machines make work easier


The ____________________________ of a machine is the amount by which a machine can multiply a force

MA = OF IF

Speed Ratio

___________________________ measures the distance an object travels in a given amount of time.

◦ ___________________________ is a measure of how the speed of an object is affected by a machine.

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Formula

The formula for calculating the speed ratio is:

Speed Ratio = Input Distance Output Distance

Example

Calculate the speed ratio:

◦ Input distance = 4m

◦ Output distance = 1m

Calculate the mechanical advantage:

◦ Input force = 45N

◦ Output force = 180N

Speed Ratio =

Mechanical Advantage =

Why are the answers exactly the same?

Did you notice that the Mechanical Advantage and the Speed Ratio’s you calculated are EXACTLY THE SAME?

What is one thing we talked about that would impact the mechanical advantage of an inclined plane?

◦ HINT: it starts with an “F”

Friction

Both the mechanical advantage and the speed ratio are the same in these calculations but in reality this would not be the case because of _____________________.

__________________ is a force that opposes motion caused by the surface roughness of materials

A rough surface creates more friction than a smooth surface…. Soooo…

The mechanical advantage will be impacted due to friction depending on the type of surface.

Think about pushing a box up a ramp. The box rubbing on the ramp would make you have to push harder in order to get that box to the top. THIS IS FRICTION!

Ideal Mechanical Advantage

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Speed ratio is the ________________________________because it is not affected by friction since it is calculating the distance that an object has to travel.

Efficiency

No machine is 100% efficient!

______________________________ is the measure of how well a machine uses energy

Formula for Efficiency

Efficiency = mechanical advantage x 100 Speed Ratio

We multiply by 100 because we want a percent!

Example

a pulley has a speed ratio of 3 and a mechanical advantage of 2

what is its efficiency?

Inefficient

_____________________________ are often very inefficient because of the many subsystems that are each affected by friction – FOR EXAMPLE:

a car engine usually has an efficiency of about 15% meaning that 85% of the energy from the gas is not used to move the car most of it ends up as heAT

Topic 2.2 – The Science of Work

Work

• __________________ is done when a ________________ acts on an

____________________ to make the object move.

– According to Science, doing your homework is not actually doing work! J

• MOVEMENT HAS TO BE DONE BEFORE WE CAN SEE ANY WORK BEING DONE!

Calculating Work

• The formula for Work is:

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80N

2m

Work = Force x Distance

W = F x d

F is the force being exerted on an object

d is the distance the object moves

W is measured in JOULES (J)

Lift a Chair

• If you lifted your chair onto your desk, how much work would you do? Assume that you

have to exert a force of 50 N to lift the chair and your desk is 0.4 m high.

Energy and Work

• ___________________ and ___________________ are closely related because without

energy, there would be no work.

– Example:

• When you ride a bike, you exert a force on the pedals.

• The chain transfers the force to the wheels causing you to move.

• YOUR ENERGY IS USED TO MOVE THE BIKE

Example

• What would the work be to lift the box up 2 m?

Work and Machines

• Using a machine does not mean that less work is done.

– You use the machine so you don’t have to exert as much force.

• BUT YOU STILL DO THE SAME AMOUNT OF WORK!

Practice Problems

1. You use a force of 40 N to push a box of books 3.2 m along the floor. How much work have

you done?

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2. Calculate the work done in the following situation: A 500 N box is lifted 0.5 m.

Topic 2.3 – The Big Movers – Hydraulics

Hydraulic Systems

• A _____________________ uses a liquid under pressure to move loads.

– A hydraulic system increases the __________________________Pascal’s Law

___________________ says that __________________ applied to an enclosed fluid is

transmitted _________________ in all directions throughout the fluid.

Pressure in Fluids

• ________________________ work because they use fluids that are under

_____________________.

– _____________________ is a measure of the amount of force applied to a given

area.

Pressure = Force Area

Units for pressure are Pa (Pascals)


• Remember:

MA = OF

IF

= 500 N

20N

= 25

• THIS IS A HUGE MECHANICAL ADVANTAGE!

Why such a huge mechanical advantage?

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Fsmall= 20N

Flarge= 500N

AREAsmall=4cm2

AREAlarge= X

• The mechanical advantage is so huge because a hydraulic system allows you to use a

______________________ on the small piston to produce a ______________________ on the large piston

Example

• Assume a small piston has an area of 4 cm2 and the force it applies to a fluid is 20 N.

What is the pressure?

• Assume a large piston has an area of 100 cm2 and a force of 500 N will raise a load.


• Soooo… the _________________ of the large piston is the ________________ the

small piston!

– _____________________ was correct – fluid does exert the same pressure in all

directions!

Fsmall = Flarge

_____ ______

Asmall = Alarge

Example

• Find the area of the large piston.

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Practice Problems

• 1. What does a pascal measure?

• 2. A hydraulic lift has 2000 N applied to an input piston that has an area of 50 cm2. The

output piston has an area of 200 cm2.

– What is the pressure on the liquid exerted by the input piston?

• 3. You use a force of 80 N to push a box of candy 3.2 m along the floor. How much

work have you done?

The formula for pressure is

p = F A

• 4. Assume a small piston had an area of 20cm2 and a force of 900N. What is the

pressure?

• 5. Assume a small piston has an area of 4 cm2 and the force it applies to a fluid is 20 N.


• 6. Assume a large piston has an area of 100 cm2 and a force of 500 N will raise a load.


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• 7. A hydraulic lift has 2000 N applied to an input piston that has an area of 50 cm2. The

output piston has an area of 200 cm2.

What is the pressure on the liquid exerted by the input piston?

Topic 3.1 – Evaluating Mechanical Devices

Intro

Mechanical devices are ___________________________ being evaluated.

Manufacturers evaluate the devices they make to find ways to improve them

Look at the Ipad. Apple has already made the Ipad 2 because they

discovered ways to improve it.

Example

Say you needed to buy anew bike.

What sorts of features would you want your bike to have?

Mountain biking?

BMX?

These features are what you would look for when you buy a bike

Bikes

All of these bikes are used for different things.

Another consideration may be cost.

It is VERY important to have a list of criteria you want to consider when buying a

mechanical device.

Evaluation

When ____________________ mechanical devices we look at certain criteria:

1. _______________________ 2. Effectiveness

3. ________________________ 4. Design

5. ________________________ 6. Considering the environment

Efficiency and Effectiveness

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You can describe the ______________________ as a number (we have learned this

already).

You can also describe it in ____________________ by saying how quickly or

easily it helps you do a task.

If a device works _______________________, it does a good job.

Example

A one-speed bike is ____________________ in carrying you from one place to another.

If is more ____________________ than walking

A 21-speed bike is just as _______________ in carrying you from one place to another

It is more ___________________ that a one-speed bike since you can change

gears for hills and use less energy.

Function and Design

The ___________________ is what the device is ____________________.

Look at the hole punch, what is its function?

The __________________ is the physical form of the device that ________________.

Why is the hole punch designed the way it is?

Evaluation for Development

_________________ is good for TWO things:

1. Helping you make a better __________________ that suits your needs.

2. To determine how it can be __________________.

Considering the Environment The _________________________ of a device on the environment should be

considered in evaluating a mechanical device.

The pop cans of the 1950’s

These cans were completely sealed and made of steel

There were NO openings anywhere on the can.

To open this can, you had to use what was called a ‘_____________________The church key

The ___________________ was a simple machine (______________________) that

used the tiny end of the triangle to cut through the steel

The church key was meant to cut two holes in the can

ADVANTAGE:

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Simple lever that required little force to open the pop

DISADVANTAGE: You needed to have one handy at all times to get the pop out.

Story time (1960’s)

______________________ forgot his church key one sunny day which was bad

because he couldn’t enjoy his pop.

He was an engineer and designed a new way for people to be able to enjoy pop.

(without a church key.

Fraze created the ____________________________Removable pull tab top

Basically, a person would bend the tab and pull back the ring like a lever.

The tab would “fail” and be pulled off the can.

THIS WAS A HUGE IMPROVEMENT FROM THE CHURCH KEY!

ADVANTAGE: Far easier and more convenient that a church key

DISADVANTAGE: Sometimes the ring detached from the tab and the can couldn’t be opened.

It also became a huge litter and safety hazard (the sharp edges on the tab)

1970’2 Push tabs invented

With billions of cans being used yearly, the environmental impact was starting to rise

from the pull tabs

A NEW SOLUTION WAS FORMED!!!

The cans would now have two holes with buttons preformed in the lid

One hole was smaller and was to be opened first.

This released the pressure in the can

The larger hole was the drinking hole and was much easier to open after the

pressure was removed.

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While the new design did help with the environmental problem from before, people were

not as happy with the new way of opening the can

Advantage: Litter problem was solved

Disadvantage: Hard to push the small button open

Consumers didn’t like using cans with two buttons.

1980’s – Non removable Tab

The non-removable pull tab eliminated the environmental problems, allowed for easy

access to the pop and was easy to use.

It was a simple machine (a lever)

The effort was placed on pulling the tab up

The fulcrum was located at the pivot point of the tab

The load was the tab being pushed into the lid

ADVANTAGES: The tab stayed attached to the can

Easy to open

DISADVANTAGES By wiggling it back and forth the tab could be broken off.

The ting may not always puncture the tab but would break off instead.

This is the best solution so far.

CSA

On mechanical devices you may see the following symbol:

It stands for the “___________________________”

The CSA is a _____________________________ that tests and

approves a wide range of products to make sure that they are safe for

consumers

Topic 3.2 – Technology develops through change

Technology Develops through change Remember the pop can and all the changes it went through?

Let’s check out a sewing machine.

It was invented in the 1800’s

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The first picture is the original sewing machine that relied on a hand crank and was only able to perform very simple stitches

The second picture was a MAJOR step forward towards the foot operated sewing machine

This allowed both hands to be free to better guide the fabric

Now the NEWEST AND BEST sewing machine can do a variety of jobs with the push of a button.

Our advancements in technology go hand in hand with out advancements in ______________.

If there wasn’t anybody trying to discover new ideas, where would we be?

Trains The maglev train in Japan are powered by electricity and run on magnetic tracks.

THEY ACTUALLY __________________! THEY NEVER TOUCH THE TRACKS!

These trains do not experience any ________________ which allows it to travel over 350 km/h.

This train resulted from physics experiments with particle accelerators, believe it or not!

Over time, society has tried to create what would be next for scientific advancements.

Robots were being created for the movies in the 50’s and 60’s and in the 70’s robots were actually being made for practical reasons.

Today many factories have now relied on robots to do the tasks that were once done by humans.

Robots perform certain tasks much faster and more efficiently than humans

Examples: diffusing bombs, welding, factories

New Technology from a Change in Society Why did the need for robots become such a big demand in factories?

Simple Answer: __________________________

In the past, people worked in boring and dangerous conditions for VERY low pay

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By the mid 1900’s, people started to demand more money and better working conditions

As the wages went up the industry started to look for ways to replace humans in certain parts of the jobs

Bottom line: robots could do humans work quicker and for less money!

New Technology from a Change in Environment Cars are being change to develop new ways to harness energy.

People are caring A TON about oil spills and environmental accidents

Technology is now starting to help meet these new goals of environmental salvation

Newer and better technology for oil spills!

Remember all the damage that happened with the BP oil spill in the gulf of Mexico.

New technology has come about now to prevent this

PRACTICE – GRADE 8Mechanical Advantage, Speed Ratio and Efficiency

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LEARNING OUTCOME #3: Students will investigate and describe the transmission of force and energy between parts of a mechanical system.

- Analyze mechanical devices to determine speed ratios and force ratios.

FORMULAS:

Speed Ratio (Gears) = # of driving teeth # of driven teeth

Mechanical Advantage = Output force Input force

A. Calculate the mechanical advantage of each of the following simple machines: 1. If we had a 1st class lever and it takes 120N to lift a 240N weight, what is the mechanical

advantage?

2. If we had a 1rd class lever and it takes 180N to lift a 180N weight, what is the mechanical advantage?

3. What is the mechanical advantage of this pulley and what would be the effort force to lift a weight that is 600N?

4. What is the mechanical advantage of the following inclined plane?

B. Calculate the Speed Ratio of each of the following simple machines: 1. Calculate the speed ratio if a driving gear has 45 teeth and a driven gear has 15 teeth. What

type of gear is this? (If the driving gear is bigger than the driven gear).

2. What is the speed ratio of the following inclined plane?

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600 N

8 cm920 cm

FORMULAS:

Speed Ratio (Gears) = # of driving teeth # of driven teeth

Mechanical Advantage = Output force Input force

20 cm

100 cm

3. What is the speed ratio of the following pulley?

4. What is the speed ratio of a pulley that has an input distance of 420cm and an output distance of 20cm?

C. Calculate the efficiency of each of the following: 1. What is the efficiency of a pulley with a mechanical advantage of 10 and a speed ratio of 5?

2. What is the efficiency of an inclined plane with a mechanical advantage of 4 and a speed ratio of 6?

3. What is the efficiency of a lever with a mechanical advantage of 7 and a speed ratio of 3?

Mechanical Systems Unit Review

Define the following terms:

1. Lever:2. Fulcrum:3. Effort Force:4. Load:5. Effort Arm:6. Load Arm:7. Class 1 Lever:8. Class 2 Lever:9. Class 3 Lever:10. Winch:11. Radius:12. Wheel and Axle:13. Inclined Plane:14. Gear:15. Gear Train:

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16. Driving Gear:17. Driven Gear:18. Fixed Pulley:19. Movable Pulley:20. Compound Pulley:21. Kinetic Energy:22. Potential Energy:

23. Give an example for each of the following:

a) Class 1 Lever:

b) Class 2 Lever:

c) Class 3 Lever:

24. Draw and label a diagram of each of the following:

a) Class 1 Lever:

b) Class 2 Lever:

c) Class 3 Lever:

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25. The Mechanical Advantage of a Fixed Pulley is ____. The Mechanical Advantage of a Movable Pulley is _____.


1. Speed Ratio:2. Efficiency:3. Work:4. Mechanical Advantage: 5. Pressure:6. Input work:7. Output work:

Give the formula for each of the following:

8. Speed Ratio =

9. Efficiency =

10. Work =

11. Mechanical Advantage =

12. Pressure =

13. What units are the following measured in?

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Work:

Force:

Pressure:

Answer the following questions: remember to include the formula

14. Jenna’s bicycle has 50 teeth on the front sprocket and 20 on the back sprocket. What is the speed ratio?

15. An electric fan exerts 80J of energy. It takes 120J of electricity to operate the fan. What is the efficiency of the fan?

16. You would like to move the TV in the living room 5m. The TV weighs 40kg. Calculate work.

17. The force exerted on a teeter-totter is 5N. The teeter-totter moves a distance of 1M. Calculate work.

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18. An electric fan exerts 80J of energy. It takes 120J of electricity to operate the fan. What is the efficiency of the fan?

19. You would like to move the TV in the living room 5m. The TV weighs 40kg. Calculate work.

20. The force exerted on a teeter-totter is 5N. The teeter-totter moves a distance of 1M. Calculate work.

21. 600 N of force is applied to a lever. The lever has an area of 0.5m2. What is the pressure?

22. A force of 500N is applied to a wheelbarrow. The load the wheelbarrow is carrying has a force of 2500N. What is the Mechanical Advantage?

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1. Pascal’s Law:2. Hydraulic Lift:3. Closed System:4. Hydraulic Systems:5. Pneumatic Systems:6. Valve:7. Pump:8. Mass Production:9. Hydrogen Fuel Cell:

10. Give two everyday examples of Pascal’s Law at work.

11. Give two examples of Hydraulic devices.

12. Give two examples of Pneumatic devices.

13. Explain how Hydraulics and Pneumatics are used in the body.

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Unit Test Date: _____________________________

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classhomeworkwebpage.weebly.comclasshomeworkwebpage.weebly.com/uploads/1/3/6/8/13685067/... · Web viewMechanical Advantage The of an inclined plane is:MA = output force (Distance

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