Issac Says: |
"Let's Learn about Potential
and Kinetic Energy!"
Potential energy exists whenever an object which has
mass has a position within a force field. The most everyday
example of this is the position of objects in the earth's gravitational
The potential energy of an object in this case is given by the relation:
PE = mgh
- PE = Energy (in Joules)
- m = mass (in kilograms)
- g = gravitational acceleration of the earth (9.8 m/sec2)
- h = height above earth's surface (in meters)
Kinetic Energy exists whenever an object which has
mass is in motion with some velocity.
Everything you see moving about has kinetic energy.
The kinetic energy of an object in this case is given by the relation:
KE = (1/2)mv2
- KE = Energy (in Joules)
- m = mass (in kilograms)
- v = velocity (in meters/sec)
Conservation of Energy
This principle asserts that in a closed system energy is conserved.
This principle will be tested by you, using the experimental apparatus
below. In the case of an object in free fall. When the object is
at rest at some height, h, then
all of its energy is PE.
As the object falls and accelerates due to the earth's gravity, PE is converted
into KE. When the object strikes
the ground, h=0 so that
PE=0, the all of the energy has to
be in the form of KE and the object
is moving it at its maximum velocity. (In this case we are ignoring
This appartus will drop a mass from different heights. When the
mass strikes the ground, some percentage of its original energy will
be absorbed by the ground.
The parameters you control are:
In addition you can measure the height of the object above the surface
by clicking on the black platform upon which the object rests. The
impact velocity of the object will also be given at each bounce.
- The Total Energy (Energy)
- The mass of the object (Mass)
- The percentage of the energy which is absorbed by the surface on
each "bounce" (EAS)
The functionality of the buttons are as follows:
- Start= Drop the ball after Energy, Mass and EAS have been set;
resume after step or pause has been selected
- Step = Drop the ball once and it rebounds to its maximum height and
- Reset = Reset experiment to intial values
- Pause = Pause the animation at any point
- Select a Mass of 5 KG
- Select an Energy of 200 J
- Select EAS = 50%
Questions to think about first:
- What is the height of the ball? (verify by measuring it)
- How high will the ball bounce on the first bounce (verify by selecting
step and then measuring the height)
- What will be the impact velocity of the ball on the first bounce
Newton Alert! Newton Alert!
- Activate the step button to run the experiment and check your answers
to the three questions above.
- Reset the experiment and set EAS to 100%. What do you expect will happen?
- Reset the experiment and set EAS to 25%. What will be the height of the
ball on the first bounce?
- Reset the experiment and set Energy to 400 and answer the question 1-3
- Reset the experiment and change the mass of the ball to 2 kg. How much
higher did the ball rise? Will the ball have a different velocity on
initial impact as in the previous case? If so, how come? If not, why not?
- Which combination of parameters do you think will allow the ball to bounce
the most number of times? Try your guesses
- Which combinations of parameters produces the lowest and highest initial
heights? Try your guesses.
Issac says: I desire to to have the impact
velocity be 6 meters/second on the third bounce
Bonus Question: What combination of Energy, M and EAS will satisfy Issac? Try to work it out in advance.