Title: Pulley Lab
Description: Students will construct
several pulley systems and see which one gives the greatest mechanical
advantage.
Materials: pulleys (single and double), mass, ring stand and
ring, spring balance
Background Information: A fixed pulley is attached
and hangs from a solid object. A moveable pulley is able, of course, to move. A
single fixed pulley changes the direction the force is applied to move an
object. It feels easier because gravity is now helping. It takes a moveable
pulley to reduce the force needed to lift the object. The mechanical advantage
of a pulley system is about equal to the number of supporting ropes on the
moveable pulleys. The mechanical advantage is always less due to friction and
the weight of the moveable pulleys.
Student
Page
Name____________________________________________
Title:
Pulley Lab
Purpose: To discover which pulley system has the greatest
mechanical advantage.
Materials: pulleys, string, ring stand and ring,
spring balance, mass.
Prediction:
Procedure:
1. Find the
resistance force of the mass using the spring balance.
2. Set up the
system below. Find the effort force and record on the data table.
3. Set up the
moveable pulley below. Find the effort force and record.
4. Set up the systems below,
find your effort force and record.
5. Calculate the mechanical
advantage for each pulley by dividing the resistance force (weight of the mass
on the spring balance) by the effort force (how hard you pulled on the spring
balance)
Data:
| Pulley System |
Resistance |
Effort |
Mech. Advantage |
| single fixed |
|
|
|
| single movable |
|
|
|
| pulley A |
|
|
|
| pulley B |
|
|
|
| pulley C |
|
|
|
Analysis:
1. Was there a difference in the mechanical advantage
for the single fixed pulley and the single movable pulley? Explain your
answer:
2. As you add pulleys, what happened to the effort force you
used to raise the mass?
3. Why would anyone use a single fixed pulley
if it does not give you a mechanical advantage?
4. A machine never
gives you something for nothing. Although the effort force is decreased,
something else is increased. What must be increased?
Conclusion:
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Updated September 18 1997 by Michelle Dumas