Download Work_Energy TN

Alabama Science in Motion
Energy: What is the Relationship between
Work and Energy?
What is the Relationship between Work and Energy?
Teacher Notes
Purpose:
The purpose of this activity is to compare the work done on a cart to the change in kinetic energy
of the cart. Determine the relationship of work done to the change in energy.
Course of Study (2005):
Physics Core:
Standard 4: velocity, force, work, kinetic energy
Lab Time: 50 minutes
Setup Time per Station: 10 minutes
Considerations:
Students will be able to…

Use a Smart Pulley to measure the motion of a cart as it is pulled by a force and use a Force Sensor
to measure the force pulling the cart.

Use DataStudio to record and display the motion of the cart and the force versus position for the cart.

Use the graphs of velocity and acceleration versus position and the built-in analysis tools of
DataStudio to determine the maximum velocity of the cart and the force of tension.

Use the graph of force versus position and the built-in analysis tools to determine the area under the
curve.

Calculate the final kinetic energy of the system.

Compare the final kinetic energy to the work done on the system.
Notes
Remind students to check the alignment of the string to make sure it is parallel to the track.
The mass of the force sensor is 95 grams (0.095 kg). You may give this to students or ask them
to measure it.
Sometimes, to find a mean/maximum value in DataStudio, a student must first uncheck ‘mean’
(or ‘maximum,’ etc.) under the Σ menu and then check it again before it is displayed on the
graph.
Revised 9/2008
Page 1 of 3
Alabama Science in Motion
Energy: What is the Relationship between
Work and Energy?
Sample Data:
The screenshots show the Graph screen for velocity versus position, acceleration versus position,
and force versus position for one trial run.
Answers to Questions:
Prediction
1.
As work is done to accelerate a cart, what will happen to its kinetic energy?
As work is done, the kinetic energy will change.
2.
How would the work done on the cart compare to its final kinetic energy?
The work done will equal the final kinetic energy.
Data
Sketch a graph of velocity versus time and a graph of force versus position for one run of data.
Include units and labels for your axes. (See Sample Data.) Data values in table below will be
variable, due to carts having slightly different masses.
Revised 9/2008
Page 1 of 3
Alabama Science in Motion
Energy: What is the Relationship between
Work and Energy?
Data Table
Total mass of cart (kg)
~ 0.600 kg
Maximum velocity
0.61 m/s
Average acceleration
0.35 m/s2
Average force
0.210 N
Area under Force curve
0.12 N·m
Calculations
Percent difference should be less than 15% (ideally less than 10%). During trial runs, this
experiment routinely resulted in 6-8% difference between kinetic energy and work values.
Questions
3.
What happens to the kinetic energy as work is done on the cart?
The kinetic energy of the system changes as work is done on the system.
4.
How does the final kinetic energy compare to the work done?
The final kinetic energy is within [10]% of the work done.
5.
The kinetic energy is measured in joules and the work done is measured in newton•meters
(N m). What is the relationship between a joule and a newton•meter?
A joule is defined as one newton of force applied over one meter, so the two units are identical.
6.
Do your results support your predictions?
Answers will vary.
Revised 9/2008
Page 1 of 3