Force and Motion

• When you jump up in the air, what pulls you back down to Earth?

• What pulls a magnet together or pushes it apart?• The answer is….

Essential Questions: What is a force?

What effect does a force have on an object?

A FORCE is a push or pull that causes a change in motion.

• Nothing can change position, speed, or direction unless a force acts on it.

• A book doesn’t just fall off of a table by itself. A force has to push it!

Forces can affect motion in several ways:

→ They can make objects start moving

→ They can make objects move faster

→ They can make objects move slower

→ They can make objects stop moving

→ They can make objects change direction

Essential Questions: What happens when two unequal forces push an object in the same direction?

What happens when two unequal forces push and object in opposite directions?

Essential Questions: What are some types of forces (friction, gravity,

magnetic force) ?•Friction- is a force that works against motion

• can make things slow down or stop, or it can keep things from moving at all

• greater between rough surfaces than between smooth one •Ice skaters glide along the ice because there is little friction between the blades and the ice.

Gravity is the universal attraction between any two objects with mass.

Essential Questions: What are some types of forces (friction, gravity,

magnetic force) ?

Magnetic Force- anything that attracts iron is considered magnetic. That’s why paper clips are attracted to a magnet. Paper clips contain iron. The force of a magnet is called the magnetic force.

A magnet is a piece of metal that pulls or attracts things which have iron or steel in them. The most common magnets are in the shape of a bar or horseshoe. The magnet is surrounded by a force field which attracts iron, especially at the poles.

Essential Questions: What are some types of forces (friction, gravity,

magnetic force) ?

Magnets are surrounded by a force field which

attracts iron, especially at the

poles.

Let’s ReviewWhich of the following is an example of trying to

increase the friction?

A. Squirting oil in hinges

B. Spreading grit on icy roads

C. Waxing the underneath of skis

Mr. Gates mops the gymnasium floor every day. When he finishes mopping, he puts up the sign shown below. The effect of which force is weakened when the floor is wet?

A. friction

B. gravitation

C. inertia

D. magnetism

Let’s Review

What is happening between these two magnets?

• A.) The magnets pull toward each other because like poles attract.

• B.) The magnets push away from each other because like poles attract.

• C.) The magnets pull toward each other because like poles repel.

• D.) The magnets push away from each other because like poles repel.

S NN S

Let’s ReviewOn which surface will a toy car travel the farthest?

A. Ice

B. Wood

C. Carpet

Let’s ReviewWhich of the following is NOT a type of force?

A. magnetic

B. friction

C. motion

D. gravity

Characteristics of Motion

• The motion of an object can be described by its:• Position• Direction• Speed• Velocity

• Position, direction, speed, & velocity can be changed by forces that act on the object.

Position• Position is the location of an object

• The dog is 2 feet away from the tree. This picture shows the position of each object: the dog and the tree.

2 feet

Direction• Motion can also be described using

directions such as north, south, east, & west. Direction of an object depends on the direction of the force. It can be measured with a compass.

• The bird flew up, the car turned left, the rabbit ran toward the gate, the dog ran away from the house

• Objects can also move toward and away.

Speed• Position and direction are helpful in describing motion.

Yet motion also occurs over time. • For example- You threw a football 20 meters. But did

the football go 20 meters in 2 minutes? 2 seconds? • Speed is the measurement of distance over time.• You can use a stopwatch to measure speed

Velocity• Velocity is the object’s speed BUT includes direction• Remember, DIRECTION includes north, south, east and

west- following the points of a compass. • For example- the football that was thrown 20 meters in

2 seconds is traveling 10 meters per second (20/2 = 10). You MUST include direction for velocity. So your answer might really be 10 meters per second west!

States the directionthe ball traveled

Measuring Motion

• Scientists use many tools to measure motion:

• Commonly used to measure direction is the compass.

• A meterstick is commonly used to measure distance between one position and another.

• A stopwatch is used to measure time

Let’s Review• Which of the following is the BEST

description of the position of the eraser?• A.) The eraser is near the

pencil

• B.) The eraser is to the left of the pencil

• C.) The eraser is 4 cm away from the pencil

• D.) The eraser is 4 cm to the left of the pencil

4 cm

Let’s Review

• What is the speed of a hockey puck that moves 45 meters in 5 seconds?

• A.) 45 meters per second

• B.) 17 meters per second

• C.) 9 meters per second

• D.) 5 meters per second

Let’s Review

• What is velocity?

• A.) speed and position

• B.) speed and direction

• C.) position and direction

• D.) direction and time

“An object at rest tends to stay at rest and an object in motion tends to

stay in motion unless acted upon by an unbalanced force.”

Newton’s First Law of Motion

Newton’s First Law of Motion

• A soccer ball doesn’t just roll across the field on its own.• It takes a force (such as a kick) to

move the ball.• Once the ball moves, it doesn’t

just move forever. Eventually it will stop.

• Earth’s gravity and friction stop moving objects.

With no net force acting upon it, an object at rest tends to stay at rest, an object in motion tends to stay in motion. Both objects will continue with the same inertia keeping the same velocity.

The acceleration of an object depends on the mass of the object and the size of the force

acting on it.

Acceleration: a measurement of how quickly an object is changing speed.

Newton’s Second Law of Motion

NEWTON’S SECOND LAW

The more mass an object has, the harder it is to accelerate.

The less mass an object has, the easier it is to accelerate.

“For every action there is an equal and opposite reaction.”

Newton’s Third Law of Motion

Forces occur in pairs- for every action there is an = and opposite reaction.

As the runner’s footpushes on the starting block (action force), the starting block is exerting a force on the runner’s foot (reaction force).

Let’s ReviewA(n) __________ is a push or a pull.

A) motion

B) velocity

C) Acceleration

D) force

Let’s Review• Which of the following is not an acceleration?

• A) stopping your bike at an intersection

• B) slowing your bike ride so you can make it up a hill

• C) riding your bike faster when you head down a hill

• D) riding your bike straight down the street at a constant speed

Let’s ReviewForces that cancel each other are called __________

forces.

• A) neutral

• B) balanced

• C) inactivated

• D) null

• Whenever one object exerts a force on another object, the second object ALWAYS exerts an equal force back on the first object.

• A.) True

• B.) False

Let’s Review

• Forces always occur in ______________.• A.) Triplets

• B.) Pairs

• C.) by themselves

• D.) either singly or in pairs

Let’s Review

Let’s Review

• Newton's first law of motion states that __________.

• A) an object will remain at rest or keep moving with a constant velocity unless a force acts on it

• B) acceleration is calculated by dividing the force exerted on an object by the mass of the object

• C) when a force acts on an object, its acceleration is in the same direction as the force

• D) when a force is applied on an object, there is an equal force applied by the object in the opposite direction

Balloon racers rely on Newton's Third Law of Motion. As the air rushes backward out of the balloon it pushes the car forward in the opposite direction with an equal force. Your job is to make the most of this force!

Balloon Racer

The rules to this activity are simple: • The car must be powered by balloons. • You can build the car out of anything (household items, craft materials,. Etc.) • It must have at least three wheels. Wheels are defined as anything that is round and goes around. • The wheels cannot be wheels from a toy car. They must be made out of something that was not originally meant to be used as wheels. • The car may not leave the ground. • The car must be capable of traveling at least 5 meters.

On race day we will set up a track in the outside hallway. You will race in pairs against other classmates. Cars that follow all of the rules will be eligible for prizes. These prizes will be given in three categories:

• Best Looking Car • Fastest Car (in first 5 meters) • Farthest Distance Traveled

There are several important things to keep in mind when designing and building your balloon racer. The first thing to do is choose the material to build the chassis or body of the car. The chassis should be both light and sturdy, for this reason Styrofoam makes a very good chassis. It is also important to design a chassis that is long enough. Short cars tend to spin out more often than longer ones. A good car should be about 30 cm long.

The second thing to do is build and mount the wheels. Wheels can be made out of anything that is round, such as CDs, caps, and lids. The hard part, however, is getting them mounted straight with little friction. If the wheels are not mounted straight or are not free to spin smoothly, the car will not perform well.

Once the wheels are mounted on the chassis it is time to put a balloon onto the car. Having the balloon attached to a pen barrel so that the air comes out in a smooth manner helps. Another helpful approach is to double up a balloon so that it is twice as thick.

If the car has a sturdy but light body, free moving wheels and a good power supply, you are well on your way to being a balloon racer champion.

Helpful Hints

Balloon Racer

Let’s Review__________ is a force that resists motion between two

surfaces.

• A) Resistance

• B) Inertia

• C) Friction

• D) Acceleration

Essential Question: Why do we need simple machines? What are the 6 simple machines?

Work means that we are exerting force and moving something.

The 6 simple machines make our work easier. We won’t have to

use as much force with our simple machines.

The Wheel and Axle

• Two or more wheels are connected by an axle

• The wheel turns with or around the axle

Pulley • A pulley is a wheel with a rope running over

it. The wheel has a groove, called a sheave, and it keeps the rope from slipping off the wheel.

• Remember, since there is a wheel in a pulley there also has to be an axle!

Lever

• There are two parts to a lever:

• The Lever Arm: the arm that moves

• Fulcrum: the support or balance that does NOT move

The Wedge

• A wedge is used to split, tighten, or secure a hold. • A wedge is usually a triangle shape with a sharp point. • If you apply force at one end, the wedge will go

between something, in this case an ax splits a piece of wood.

• A wedge is a special kind of inclined plane made of two slopes, back to back.• Wedges can be used to move things apart.• Wedges can change the direction of the applied force. 

The Inclined Plane

• The inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised.

• A screw is a rod with an inclined plane wrapped around it.The spiraling inclined plane forms ridges which are called threads.

Let’s ReviewWhich of the following is NOT a simple

machine?

A.) inclined plane

B.) wedge

C.) elevator

D.) screw

Let’s ReviewA fork is an example of a:

A.) pulley      

B.) wedge      

C.) wheel and axleD.) lever 

Let’s ReviewA saw, a knife, and a doorstop are all

examples of what type of simple machine?

A.) inclined plane

B.) wedge

C.) pulley

D.) screw

A teeter totter on the playground is an example of what type of simple machine? 

A.) lever      

B.) wedge      

C.) pulley

D.) inclined plane

Let’s Review

Standards Covered• SC.C.1.2.1- The student understands that the

motion of an object can be described and measured.

• SC.C.1.2.2- The student knows that waves travel at different speeds through different materials.

• SC.C.2.2.1- The student recognizes that forces of gravity, magnetism, and electricity operate simple machines.

• SC.C.2.2.4- The student knows that the motion of an object is determined by the overall effect of all of the forces acting on the object.