Name__________________________________
Physics 206
Mr. Dristle
Momentum in Collisions
Prediction Sheet
Pre-demonstration questions:
1.
What is momentum?
2.
How do you figure out how much momentum an object has?
3.
What is the “Law of conservation of momentum”?
Demonstration #1: Mass is added to a moving object.
4.
What do you predict will happen to the velocity of the moving cart when a
bowling ball is dropped (placed) into the crate on the cart as it passes by?
5.
Should the moving cart have more, less, or the same amount of momentum after
the mass of the bowling ball is added to it?
(Think carefully: What’s supposed to be conserved? momentum or velocity)
6.
As the demonstration is performed, record your observations here.
Name__________________________________
Momentum in Collisions
Page 2
Demonstration #2: A head-on collision between two moving objects
7.
What do you predict will happen to the crate and the cart it is resting upon, when
they collide head-on with a bowling ball that was moving straight toward them?
8.
Explain how Newton’s Laws of Motion are consistent with your prediction.
9.
As the demonstration is done, record your observations here.
Demonstration #3: A stationary object is struck from behind by a moving object.
10.
What do you predict will happen to the momentum of the cart and what has been
placed on the cart when it struck from behind?
11.
Using this as an example, explain how momentum can be transferred between
objects without violating the law of conservation of momentum.
12.
As the demonstration is done, record your observations here.
Name__________________________________
Physics 206
Mr. Dristle
Momentum in Collisions
Conclusions
ADDED MASS SCENARIO
Watch the demo and considering the following points:
13. Compared with the beginning, how much mass is in horizontal motion by the end of the
demonstration? (more or less or the same)
14.
Recall your prediction regarding what would happen to the velocity and the momentum of
the moving cart. Describe in terms of your observations and Conservation of Momentum
how your prediction was either justified or was in error and why.
For extra credit: Why doesn’t the vertical momentum of the bowling ball (as it is dropped into the
cart) count for anything in this demonstration?
FRONT END COLLISION SCENARIO
Watch the demonstration and then answer the following questions.
15. What happens to the direction of the bowling ball after the impact? (reversed direction or
same direction or completely stopped)
16.
What happened to the direction of the cart after the impact? (reversed direction or same
direction or completely stopped)
17.
Recall what you predicted would happen to the crate. If your prediction was correct, say so
here. Otherwise, write down what really happened.
18.
How are Newton’s Laws of motion related to the principle of Conservation of Momentum?
**HINT Inertia and momentum are related to one another…
For extra credit: Explain how two objects that individually have a lot of velocity and momentum
before a head on collision can have so little (if any) velocity and momentum after the
collision. Isn’t the total momentum before the collision supposed to be equal to the total
momentum after the collision? How can this be?
Name__________________________________
Momentum in Collisions
Page 4
REAR END COLLISION SCENARIO
Consider the following scenario: A driver in a car comes to a complete stop at an intersection. The
driver behind the stopped car does not stop in time and hits the stopped car. This kind of
collision, as experienced by the stopped car, is called a rear end collision.
**NOTE for your reference, the cart is heavier than the bowling ball
19.
What happens to the “driver” of the stopped car, in this demonstration?
If his neck and spine were as flexible as that of a real human being, which direction would
the head move upon impact? (forward or backward or not moving relative to the car)
20.
Explain the motion of the cart and its “driver” after the collision in terms of both Newton’s
Laws of motion and the law of conservation of momentum.
21.
Think of some ways in which you could adapt these demonstrations for your own use when
you become the teacher in an elementary classroom. There are plenty of examples on the
web. Some materials that have been used before would include skateboards, toy cars, dolls,
and even eggs. More importantly, pick out an idea associated with safety such as ‘why we
should wear seat belts’ or ‘the purpose of the headrests in cars’. Describe how you could
use a demonstration to not only teach safety but laws of physics as well.