Simple Machines
Pulley Up
Problem:
How does the type of pulley affect its mechanical advantage?
What type of pulley system gives the greatest mechanical advantage?
Description:
A pulley is a wheel with a groove along its outer edge that
holds a rope or, in this case, a string. Two or more pulleys are
usually used together to reduce the amount of force needed
to lift a load.
However, as with all simple machines the same amount of
work is necessary for the load to reach the same height as it
would without the pulleys. The size of the force is reduced,
but it must act through a longer distance.
Background: Use the information above when writing the background.
Variables: Identify the three variables in this experiment. Explain how the variables will be changed, measured or
controlled.
How will you change it?
Independent Variable/s
The one you change
How will you measure it?
Dependent Variable
The measurable result you are
looking for
Constants/Controlled Variables
List the factors you keep exactly
the same in all parts of the lab
How will you control it?
Hypothesis: Write a hypothesis for this experiment.
Materials:
ring stand and ring
pulleys
string
Newton-meter
Digital Balance
Mass
MA = Resistance
Effort
Method:
1. Measure 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 this movable pulley system. Find the effort force and
record on the data table.
Figure 1 Pulley A
Figure 2 Pulley B
3. Set up the systems below, find the effort force for each and record.
Figure 3 Pulley C
Figure 4 Pulley D
Figure 5 Pulley E
4. 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). Show a sample calculation.
Processing of Data:
A. Data Table
Pulley System
Resistance
(weight of
mass/load)
in Newton
Effort (pulling force in Newton (N)
Trial 1
A single fixed
B single movable
C
D
E
B. Summary of Observations
Trial 2
Trial 3
Average
Mechanical
Advantage (MA=
Resistance/Effort)
Conclusion:
1. Answer your aim and support your answer with detailed evidence (your results). Provide an explanation of your
results.
2. Write a paragraph explanation of the results and the “science” behind the results.
Additional guide questions:
a. Was there a difference in the mechanical advantage for the single fixed pulley (A) and the single movable pulley (B)?
Explain your answer.
b. As you add pulleys, what happened to the effort force you used to raise the mass?
c. Why would anyone use a single fixed pulley if it does not give you a mechanical advantage?
d. A machine never gives you something for nothing. Although the effort force is decreased, something else is increased.
What must be increased?
e. How does a pulley make the Work easier? How is this simple machine used in the real world?
Evaluation: In the table provided below, identify errors and explain the effects these errors had on the results. Provide
suggestions for improvement. State whether your experiment was a fair test.
Weaknesses/Errors
How it affected the results
Improvement
Overall, state whether these errors altered the final outcome of the experiment. (Was it a fair test?)
CHECKLIST
Part 1a: Design Plan
Title and Date are provided; properly headed
Background links to the topic on pulleys and mechanical advantage
Aim is provided.
Variables (independent, dependent, constant) are correctly
identified
Hypothesis: Qualitative/Quantitative predictions provided and
follows If, then… because…. format
1b: Appropriate tools and techniques
Materials are listed with necessary quantitative information
(amount and size)
Method - consists of easy to follow numbered steps (not written as
a narrative). Uses active voice.
Diagram of apparatus is neatly drawn and labeled appropriately;
ruler and pencil drawn (labels down right hand side)
1c: Presentation of data
Data table is properly headed, shows results for the variables and
reflects average of the 3 trials
Part 2a: Conclusion
Aim is answered and supported by the data to prove hypothesis
Provides an explanation of the results.
Explained the science behind the experiment.
Uses passive voice.
2b: Evaluation
Identifies weaknesses in the method and provides suggestions for
improvement
Explains how the identified errors (if any) altered the final outcome
Provides suggestions for future experiments.
Organization
Presentation-Typed, neatness; correct format; basic proofreading
SELF
PEER
TEACHER