WORK AND ENERGY CHAPTER 12. 9.1 WORK, POWER, AND MACHINES This is an ad which used a Rube Goldberg type application….many simple machines working together.

WORK AND ENERGY

CHAPTER 12

9.1 WORK, POWER, AND MACHINES

• This is an ad which used a Rube Goldberg type application….many simple machines working together to accomplish a simple task: http://www.daboyz.org/honda/

• The film is real and took 606 takes (no digital imaging). Two cars were disassembled for the parts in the film.

• The film cost six million dollars and took three months to complete.

WORK - ___________________(W = F x d)

TRYING TO LIFT THE OBJECT BUT IT DOES NOT MOVE….IS WORK BEING DONE?

JOULE – a unit to describe work one JOULE = a NEWTON moving one METER

If you lift one ______ from your waist to over the top of of your head you have done one JOULE of work.

POWER - _________________(P = W/t)

Running up the steps and walking take the same amount of work….but which requires more power?

WATT – a unit to describe powerone WATT = one JOULE of work in one SECOND

If you quickly move an object weighing one newton from your waist to over your head in one ______ you have done one WATT of work.

MACHINES make work easier but do not make less work.

WORK INPUT ALWAYS EQUALS WORK OUTPUT.

MECHANICAL ADVANTAGE - _______(MA = output force/input force)

or(MA = input distance /output distance)

Machines with a MA of more than one multiply force and those with a MA of less than one increase the distance and speed.

1. A spring scale is used to measure force and the unit of force is…

1. Joules

2. Watts

3. Newtons

2. A meter stick is used to measure distance and the unit is …

1. Newtons

2. Meters

3. Grams

3. Work is equal to force times distance and the label is …

1. Newtons

2. Grams

3. Joules

4. Power is equal to work divided by time and the label is …

1. Watts

2. Joules

3. Newtons

5. Power is the ___ at which work is done.

1. Speed

2. Rate

6. Not including friction the work into a machine is always ___ work out.

1. Less than

2. Equal to

3. Greater than

7. Including friction the actual mechanical advantage is always ___ the ideal advantage.

1. Greater than

2. Equal to

3. Less than

12.2

Make a chart in your notebook similar to this one and label it SIMPLE MACHINES. Place the name of each simple machine at the top of a column and then draw a picture of each under its name. Then identify several example of each type of simple machine.

Lever Pulley Wheel & axle

…. …. …..

E R

Fly swatter

THE LEVER(THREE CLASSES)

• FIRST - _____ in the middle.

• SECOND - _____ in the middle.

• THIRD - ______ in the middle.

THE PULLEY(A MODIFIED LEVER)

A SINGLE FIXED PULLEY has a MA of ____.

A SINGLE MOVABLE PULLEY has a MA of ___.

MULTIPLE PULLEYS can have various MA’s.

THE WHEEL AND AXLE(A LEVER OR PULLEY ON A SHAFT)

• Mechanical Advantage depends on size of wheel and size of axle.

• Some are designed for power.

• Some are designed for speed.

THE INCLINED PLANE

A long gradual slope has a larger MA than a short steep slope.

THE WEDGE(A DOUBLE INCLINED PLANE)

• The mechanical advantage depends on the length of the slope and how wide the wedge is. (if length to height ratio is greater, then greater MA)

• Using wedge is like pushing a ______, instead of pushing an object on it.

THE SCREW(AN INCLINED PLANE WRAPPED

AROUND A CYLINDER)• Steepness of slope determines

the M.A.

COMPOUND MACHINES - ______

Homework

• Make a pneumonic device for the 6 simple machines.– Louis Plank Was

• Complete #2-8

12.3 ENERGY

• by MICHELANGELO

Creation of the Sun, Moon, and Plants

Energy is expressed in joules

POTENTIAL ENERGY - _________

• Called energy of ______

• GRAVITATIONAL POTENTIAL ENERGY depends on mass and height. More MASS or more HEIGHT equals more potential energy.

KINETIC ENERGY -_____________

Depends on mass and speed but more on speed.

EXAMPLES OF POTENTIAL AND KINETIC ENERGY

MECHANICAL

GRAVITY

ELASTIC

MOVING AIR(Bernouli)

SPRINGS

NONMECHANICAL

LIGHT

ELECTRICAL

CHEMICAL

NUCLEAR

SOUND

HEAT

Section Review

• # 1-5

12.4 CONSERVATION OF ENERGY

POTENTIAL ENERGY CAN BECOME KINETIC ENERGY

A ____ at the top of a hill has potential energy.

KINETIC ENERGY CAN BECOME POTENTIAL ENERGY

A _____rising to the top of a hill has kinetic energy.

OTHER ENERGY CHANGES

When potential and kinetic energy transformations are taking place some energy is “lost” (transferred) as HEAT energy or SOUND energy.

The LAW OF CONSERVATION OF ENERGY

Energy cannot be ______ or _______.

EFFICIENCY OF MACHINES - _______________________

Not all of the work done by a machine is useful work.

No machine is 100% efficient.

Perpetual motion machines are impossible.

Section Review

• #1-3, 5 & 6

Ch 12 Test Review• Work, power, energy, MA: formulas and units

• 6 types of Simple Machines

• Types of energy

• Energy conserved & converted (applied to a system, such as a roller coaster)

• There may be a short answer section on the next test.

• Test dates on back board