1. Pulleys

2. Pulleys
A pulley is a simple machine that uses grooved wheels and a rope to raise, lower or move a load.

3. Draw the diagram and label the arrow.
FORCE = N
Using your spring scale, lift the object up straight up.
Record the amount of force needed.
load

4. Fixed pulley
Draw this diagram in your notes. Label the arrows.
load

5. Spring
scale
attaches
here
Now, using one pulley,
attach the object to one end of the string. On the other, attach the spring scale.
Gently pull, using a constant motion to lift the object.
Record the force needed.

6. Did the amount of force needed to lift the load change?
Fixed pulley
NO!
Amount of force stays the
same, but the direction of
the force changes with a
fixed pulley.
load

7. Draw this diagram and label the arrows.
movable
pulley
load

8. What was the force needed to lift the load with one movable pulley?
A moveable pulley
decreases the amount
of force needed to lift
the load.
The cupboard is taking
part of the load, so
less force is needed.

9. fixed pulley
load
movable
pulley
Draw the diagram and label the arrows.

10. Attach
spring
scale
Now we will use 2 pulleys. Tie one end of the string to a handle on the cupboard. Thread in the string on the pulley that attaches to the weight. Then thread the string into the pulley already attached to the handle. Finally, attach the spring scale to the free end. Again, pull in a constant motion. Record the force needed to lift the weight.

11. What was the amount of force need to lift the load
with a fixed and movable pulley?
The more pulleys, the less force needed to
lift a load.

12. The only thing that changes
is the direction of the force
you have to apply to lift the
weight. You still have to
apply 100 pounds of force to
lift the weight.

13. With the pulley tied to the cupboard, ½ the force is carried by the cupboard.

14. By using two pulleys the weight is split equally
between the two pulleys, so each one holds only
half the weight. You only have to apply 50 pounds
of force because the ceiling exerts the other 50
pounds of force.