Interactive
Lecture Demonstration
Prediction
Sheet—Momentum
Directions: Click here to download the Prediction Sheet. Write
your name at the top to record your presence and participation in these
demonstrations. For each demonstration below, write your
prediction on this sheet before making any observations. You may be asked to
send this sheet to your instructor.
|
Demonstration
1:
A ball is dropped to the ground. On
the diagram to the right, draw the force(s) acting on the ball as it is
falling. Is there a net force acting on the ball as it falls? Is the momentum of the ball conserved
(constant) as it falls? If you think momentum is conserved, state why. If not, describe a system, that includes
the ball, in which the total momentum is conserved. Only after you have made your predictions click here to
observe the results. Compare to your predictions and explain any differences. |
(The ball is in
the air, falling)
|
|
Demonstration 2 A ball is
dropped to the ground. The ball hits the ground and bounces up. It has the
same speed just before and just after it hits the ground. On the diagram to the right, draw the
force(s) acting on the ball while it is
in contact with the ground. Is there a net force acting on the ball when
it is in contact with the ground? Is the momentum of the ball conserved
(constant) from just before it hits the ground until just after it leaves the
ground? If you think momentum is conserved,
state why. If not, describe a system,
that includes the ball, in which the total momentum is conserved. Only after you have made your predictions click here to
observe the results. Compare to your predictions and explain any differences. |
(The ball is in
contact with the ground, bouncing.)
|
|
Demonstration
3:
Two objects A and B, of equal mass, collide and bounce apart. One of the
objects is initially traveling to the right, and the other object is
initially at rest. In the lower half of the box on the right, draw the
force(s) acting on each object as they
collide (while they are in contact with each other). How do the
magnitudes of these forces compare? Compare the
momentum of either object just before
the collision to its momentum just
after the collision. Compare the total (combined) momentum of the two objects before the collision to
their total momentum after the collision. Only
after you have made your predictions, click here
to view the forces. Then click here to see
a video of the collision, including measurements of the velocities. Compare
the results to your predictions. Explain any differences. Was
momentum conserved? Explain. |
|
|
Demonstration
4:
Two objects A and B, of equal mass, collide and stick together. One of the objects is initially traveling to the
right, and the other object is initially at rest. In the lower half of the
box on the right, draw the force(s) acting on each object as they collide (while they are in
contact with each other). How do the magnitudes of these forces compare? Compare the
momentum of either object just before
the collision to its momentum just
after the collision. Compare the total (combined) momentum of the two objects before the collision to
their total momentum after the collision. Only
after you have made your predictions, click here
to view the forces. Then click here to
see a video of the collision, including measurements of the velocities. Compare
the results to your predictions. Explain any differences. Was
momentum conserved? Explain. |
|
|
Demonstration 5: A small object
collides with a much more massive object initially at rest and bounces off of
it. Assume that friction is so small that it may be neglected. In the box to
the right, draw the force(s) acting on each object as they collide (while they are in contact with each other). How
do the magnitudes of these forces compare? Is the momentum
of the small object conserved? Is the momentum
of the large object conserved? Is the combined momentum of the two objects
conserved? Only
after you have made your predictions, click here
to view the forces. Compare
your results to your predictions. Explain any differences. |
|
