work. force force - a push or pull –you exert force on a pencil when you write forces are...

WORK

Force

• force - a push or pull– You exert force on a pencil when you write

• Forces are described by how strong they are and in what direction they are going

vocabularyword!

Unbalanced Forces

• unbalanced forces - cause an object will change the object’s motion– start moving– stop moving– change direction

vocabularyword!

Unbalanced Forces

Balanced Forces and Motion

• Forces exerted on an object do not always change the objects motion

• Balanced forces – equal forces acting in opposite directions – If forces are equal but opposite, the object

will not move

vocabularyword!

Balanced Forces and Motion

Work• work - when you exert a force on an object

and it moves

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Work

• Work is only done if an object moves some distance– Holding something is not work even though it

makes you tired

No Work

Work

• Work or no work?

no work workworkwork

Calculating Work

• The amount of work done depends on both the amount of force you exert and the distance the object moves.

• Work is measured in joules– A joule is the amount of work you do when

you exert 1 Newton of force to move an object 1 meter

Work = force x distance Write down this equation

Calculating Work

• How much work is done if a 2N of force is used to move a box 4m?

– Work = force X distance– Work = 2N x 4m

8 J

Calculating Work

• A hydraulic lift exerts a force of 12,000N to lift a car 2m. How much work is done on the car?

– Work = force X distance

24,000 J

Calculating Work

• You exert a force of 0.2N to lift a pencil off the floor. How much work do you do if you lift it 1.5m?

– Work = force X distance

.3 J

• Who is doing more work to move the barrel?

• Who has to use more force to move the barrel?

Work = 6m x 2N

Work = 3m x 4NWork = 12J

Work = 12J

They are doing the same amount

The man with the shorter ramp

Activity 1 Apply a quick push to the block of

wood to make it move 100cm.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

object’s motion

pushing force

Activity 2 Apply a force to the block to lift it

100cm.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

Activity 3 Apply a constant force to the block to

move it 100cm.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

Activity 4 Hold a book at the same level for 15

seconds.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

Activity 5 Apply a constant downward force to

the desk for 15 seconds.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

Activity 6 Apply a pull to the block to move it

100cm.

Diagram the situation. Make sure you show arrows for your force and the direction of motion of the object.

Ramp or No Ramp Materials

block spring scale

board meter stick

Procedure

1. Attach the block with the eyelet to the spring scale.

2. Using the spring scale, lift the block into the air to a height of .5m (50cm). Record how much force was used. Make sure you read the spring scale during the lift, not when you stop at .5m.

3. Build an inclined plane (ramp) with a height of .5m. Record the length of the inclined plane.

4. Attach the spring scale to the block with the eyelet and pull it up the ramp.

5. Record the amount of force it took to move the shoe.