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