Download Virtual Physics Lab Workbook

Name
Date
Class
Lab 12: Energy Conversions
Purpose
To measure the conversion of energy between potential and kinetic using an
inclined plane
Background
Knowing how energy behaves is even more important than knowing what it is.
The law of energy conservation states that energy cannot be either created or
destroyed. So the energy of a system must remain the same before and after
things happen to it. A person walking to the top of a burning building has to
work to climb the stairs. The energy from the work is then stored in potential
form because of the force of gravity pulling her down. If she were to jump from
the burning building onto a fire fighters’ trampoline, her potential energy
would be converted into kinetic energy as she was falling. As she speeds up
while falling, her potential energy decreases because she is closer to the ground
and her kinetic energy increases as her speed increases. When she hits the
trampoline she will slow down and her energy will convert into vibrations
(elastic potential energy), heat and noise.
Skills Focus
Making generalizations, interpreting data, applying concepts, drawing
conclusions
Procedure
1. Start Virtual Physics and select Energy Conversions from the list of
assignments. The lab will open in the Mechanics laboratory.
2. The laboratory will be set up with a ramp, a ball on the ramp, and a plunger
on the ball. Using the Force button to hit the plunger, you will push the ball
up the ramp. The ball will stop at some point and come rolling back down
the ramp.
3. You will need to record and use the data from the experiment. Click on the
Lab Book to open it. The click the red Recording button. When the Force button
is clicked, the data selected with the check marks will be automatically
recorded.
Energy Conversions
ISBN 1-269-73240-4
4. Click the Force button to hit the ball up the ramp. Then watch the ball fall
back to the bottom.
Energy Conversions
39
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.
Name
Date
Class
5. Click the link in the lab book that contains your data. You may want to copy and
paste it into a spread sheet program. From the data you should find five
different locations of the ball and compare the ball’s potential and kinetic
energies at those points. First you will find and record the different velocities
and the heights at which the ball had those velocities. The beginning was when
the ball first got hit. Record the ball’s velocity right after it was hit (the first data
point where velocity ≠ 0.) Then find a middle height in the data and record it
and the velocity of the ball at that height. Do the same for the top, the middle
on the way down, and then the bottom again. Record the information in Data
Table 1.
Data Table 1
Ball Position
Height (m)
Velocity (m/s)
Beginning bottom
Middle going up
Top
Middle coming down
End bottom
6. Now you can calculate the gravitational potential energy and the kinetic
energy of the ball at the different positions. Recall that gravitational
potential energy is due to the work of lifting the ball against gravity. So you
only need to know the height of the ball off the ground y(m). Record your
calculations in Data Table 2. Use the equation:
PE = mgh
where m is mass of ball, g is the acceleration due to gravity, and h is height of
ball from ground.
7. Recall that the kinetic energy of an object depends on its mass and the speed
or velocity that it is moving. Calculate the kinetic energy using the equation:
KE=
1
mv2
2
where m is mass, and v is the velocity of the ball.
Data Table 2
Ball Position
Potential Energy
Kinetic Energy
Energy Conversions
Starting bottom
Middle going up
Top
Ending bottom
40
Energy Conversions
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.
ISBN 1-269-73240-4
Middle coming down
Name
Date
Class
Analyze and Conclude
1. Making Generalizations
energy?
What determines potential energy? Kinetic
2. Interpreting Data
Why?
When did the ball have the most potential energy?
3. Interpreting Data
When did the ball have the most kinetic energy?
4. Applying Concepts What is the relationship between the PE at the top of
the ramp, and the KE at the bottom of the ramp?
Energy Conversions
ISBN 1-269-73240-4
5. Drawing Conclusions Where did the energy go from the top of the ramp
to the bottom? Explain the motion of the ball throughout the experiment in
terms of potential and kinetic energy.
Energy Conversions
41
Virtual Physics Lab Workbook, by Brian F. Woodfield, Steven Haderlie, Heather J. McKnight, and Bradley D. Moser. Published by Pearson Learning Solutions.
Copyright © 2008 by Pearson Education, Inc.