Conservation of Energy Lab
Name_____________________Pd______
Lab Partners: _____________________
_____________________
_____________________
Purpose:
In this experiment, the law of conservation of energy will be investigated by comparing the starting potential
energy of a pendulum to its kinetic energy as it swings through its lowest (equilibrium position) point.
Testable Question:
Does the kinetic energy of a pendulum at the bottom of its swing equal the change in its potential energy from
its drop position?
Materials:
1 200g standard mass
1 length of string at least 0.5m long
1 meter stick
1 meter stick
approx. 8 meter of ticker tape
ring stand
2 C-clamps
masking tape
Procedure:
1. Measure the mass of a pendulum bob and record in the data chart.
2. Assume that the space between any two ticker tape dots takes 1/60th of a second to create
3. Attach the end of the tape to the pendulum bob, as shown in the illustration.
Carbon disk
200 g
mass
Ring stand
Ticker timer
Ticker tape
With NO
SLACK
4. Measure the height that the pendulum bob is above the table (not above the ring stand base) when the
pendulum is in its vertical equilibrium position.
5. Displace the pendulum to one side until the vertical distance between the pendulum and the table is
higher than it was at the equilibrium position
6. Measure the pendulum bob’s new height above the table top, start the timer and release the pendulum.
7. When the pendulum has swung over to the other side and is just starting back down, stop the pendulum and
the ticker timer and examine the tape.
8. Find the largest space on the tape and measure it.
9. Convert the distance measurement to meters and calculate the maximum speed that the pendulum achieved
during its swing by dividing the distance by the time that is associated with a single interval on the paper
(time/space = 1/60th second).
10. Using the speed calculated in the previous step, calculate the maximum kinetic energy of the pendulum
using the relationship:
KE = ½ mv2
11. Repeat the above procedure, raising the pendulum bob to four other different heights.
12. Calculate the potential energy of the bob before it started its swing by using:
13. Compare the initial PE for each swing to the final maximum KE for each swing by calculating the %
difference for each trial, using the PE as the truer of the two values.
Suggestions and Techniques:
 Use a pendulum that is at least 0.5meter long.
 When measuring the distance between the pendulum (the bob) and the top of the table, you
may measure to any part of the pendulum bob, as long as the same part of the bob is used for
each measurement.
Data: Mass of pendulum bob _________ grams __________ kilograms
Rest height of bob above table : ________cm
Trial
height of
drop from
table (cm)
h
(cm)
h
(m)
PE (J)
1
d max
(cm)
d max
(m)
t (sec)
vmaximum
(m/s)
KE (J)
% diff.
of PE
and KE
1/60
2
3
4
5
6
7
8
Ave % Differ.
Sample Calculations:
Quantity
Formula
g to kg
cm to m
h
PE
Maximum velocity
KE
% difference
(PE - KE) 100
PE
Substitution
Answer w/ Units
Questions:
1. When you compare the average values of your PEs to the value of the KEs for each swing, what trend/s do
you notice?
2. What factor/s might account for the trend/s you noticed in #1 above?
3. On a separate sheet of paper, explain which kind of energy (PE or KE) that ONE of those factors would
affect and how it would affect that energy. (You may use labeled diagrams, explanations, or a calculation to
show this)
4. How closely did your change in potential energy match your maximum kinetic energy? Justify your answer
5. Overall, are you convinced that the law of conservation of energy works? Explain why or why not.
6. What other way might you use to test the law of conservation of energy? Briefly describe a possible set up
that could be used to test the law.