Name: Period:

Pulley Lab

Pulleys are simple machines that can be used to change the direction of a force, to reduce the force needed to move a load through a distance, or to increase the speed at which the load is moving. Pulleys do not change the amount of work done. However, if the required effort force is reduced, the distance the load moves is decreased in proportion to the distance the force moves. Pulley systems may contain a single pulley or a combination of fixed and movable pulleys.

Procedure

1.You will be using fourdifferent pulley systems that have already been set up. Make sure the strings are attached to the pulleys as needed (see picture). Please leave the pulley system the same way you found it. Read steps #2-4 before you begin recording data.

2.Starting with Pulley System 1, use the 500g mass and carefully raise the mass by pulling on the spring scale. Record the measurement in the data table.

3.Measure the height, in centimeters, that the mass is lifted. Record in data table one.

4.Measure the distance, in centimeters, that the spring scale is moved to raise the weight. Record this value in the data table.

5.Repeat steps 2-5 except using the 1000g mass. Be sure to record all values.

6.Move on to the next three Pulley Systems following the same proceduresabove for each different system.

Data Table
Pulley System / Mass (g) / Number of Pulling Strings / Force[F]
(N) / Height [h] (cm) / Distance [d] (cm)
1 / 500g
1000g
2 / 500g
1000g
3 / 500g
1000g
4 / 500g
1000g

Calculations

1.Calculate the weight (Fg) of each mass by multiplying its mass in kilograms by gravity. Record.

2.Calculate the Work Input by multiplying the force (F) by the distance (d), in meters, moved. Record.

3.Calculate the Work Output by multiplying the Weight (Fg) by the height (h), in meters. Record.

4.Calculate the Efficiency by dividing the Work Output by the Work Input, then multiply by 100. Record.

Calculations Table
Pulley System / Mass (g) / Weight[Fg] (N) / Work Input (J) / Work Output (J) / Efficiency (%)
1 / 500g
1000g
2 / 500g
1000g
3 / 500g
1000g
4 / 500g
1000g

Analysis

1.For this lab, list three possible reasons that the efficiency is never exactly 100%? Explain why it is never 100%. (4 pts)

2.What happens to the force, F, as the mechanical advantage gets larger? Why? (2 pts)

3.How does increasing the mass affect the efficiency of the pulley system? (2 pts)

4.How does changing the number of pulling strings affect the force, F, that is needed? (2 pts)

5.Explain why the following statement is false: A machine reduces the amount of work you have to do. What does a machine actually do? (2 pts)

6.In the space provided, sketch a pulley system that can be used to lift a boat from its trailer to the rafters of a garage, such that the effort force would move a distance of 60m while the load will move 10m. (2 pts)