Potential & Kinetic Energy of a
Marble Roller coaster
The energy of the marble on the roller coaster is a combination of potential and kinetic
energies. Potential energy, also known as stored energy, depends on the height of the
marble. Kinetic energy is related to motion and depends on the speed of the marble.
Below are the equations for potential and kinetic energies. Note that when you use
these equations, the resulting units equal the energy unit joules. One joule is equal to
one kilogram-m2/sec2. In the space provided, list what each variable means, and what
units it is measured in.
Potential Energy-
PE=
m=
g=
h=
measured
measured
measured
measured
in
in
in
in
PE  mgh
Kinetic Energy-
KE=
m=
v=
measured in
measured in
measured in
1
KE  mv 2
2
Directions:

Set up your rollercoaster at your station. Place the rollercoaster on the 5th hole.

Only one photogate will be used and will be placed at 6 different positions
(column 1)
Example of Set-up
A
D
B
C
E
F
Dotted line is
the lowest part
of track - not
the table!

Make sure to place the photogate flat against the rollercoaster

Measure from the table to middle of the ball in cm then subtract 10 cm
(This is the distance the bottom of the track is above the table) then record
(column 2) and convert the cm into meters in the next column. (column 3)

Using the data collected with the marble rollercoaster, calculate velocity using
the distance of travel (column 6) and time (column 5). Show work in column
7.

Calculating the KE and PE at each location on the rollercoaster is very
important. Complete KE (column 8) by using the mass (column 4) and
velocity (column 7)
Complete PE (column 9) by using the mass (column 4), height (column 3), and
10 m/s for gravity

The total energy at each position or MECHANICAL ENERGY on the
rollercoaster is calculated by adding the potential and kinetic energies at each
position. Find the total energy at each position and record the result in column
10.
ENERGY DIAGRAM – Please put all of the KE, PE, and Total Energies at each
position in the chart below.
KE =
PE =
Tot E =
KE =
PE =
Tot E =
KE =
PE =
Tot E =
KE =
PE =
Tot E =
KE =
PE =
Tot E =
KE =
PE =
Tot E =
Analyzing the Results:
1)
From your graph, what can you say about the energy of the marble? Write a
short paragraph describing the energy of the marble at different places on
the track. In your discussion include:
a. The changes in kinetic energy
b. The changes in potential energy
c. What happens to the sum total of kinetic & potential energy.
2)
What percentage of the marble’s energy is left at the end of the roller coaster
just before it stops (or at the last place you measured)?
3)
Using your data fill in the Kinetic and Potential Energy that was observed at
each of the locations on this diagram. What are some common trends that
you observed?