Conservation of Momentum
Momentum: A quantity that expresses the motion of a body and its resistance to slowing down. It is equal to the product of the object's mass and velocity.
We use the term momentum in daily life often. Let's say you've started cleaning your room and you don't want to stop quite yet, because you've built up momentum. It's the same idea.
If you read the definition it reminds you a little of inertia, doesn't it? The idea that something moving will keep on moving. But if we stop that something, the energy of motion doesn't get destroyed, just transferred.
The Challenge: You're going to be simulating a car crash!
The Tools: The dynamics carts, bricks, meter sticks, masking tape and a fairly big space on the floor where you won't get stepped on.
The Tricks of the Trade:
Since we don't have a good way of measuring velocity in the classroom, we are going to consider velocity and distance to be directly related. Do you agree it is reasonable to expect things with higher velocities to go further?
Directions:
Take a look at the two
dynamics carts you have. One is a
"dud". The other has an
exploding mechanism. To activate
the exploding mechanism, carefully push the rubber tipped plunger into the cart
until its notch hooks on the edge of the car. To release the exploding mechanism, gently tap the red
button on the top of the cart.
Please only do this if the cart is sitting flat.
The exploding mechanism
will allow us to more accurately control and recreate the force of the impact
between the carts. Determine with
your partner which setting would produce the most force and which would produce
the least.
Push the plunger in the
car so it will release the least amount of force. Put one brick on each cart. Place the "dud" cart close enough to the exploder
so that it will be "hit".
This will be the same as if they were in a head-on collision going
the same speed.
Mark the start spot of
each cart on the floor with masking take.
Use a meter stick to tap the red release button being sure not to give
the cart a push at the same time.
(This can be tricky and may take some practice.) Record the distance each cart travels
in a certain amount of time. (You
decide. 5 – 10 seconds seems reasonable, but I leave it up to you.) Record your data and repeat with the
following situations.
·
Both carts = 1 brick
(as described above)
·
Exploder cart = 1
bricks, dud = 0 bricks
·
Exploder cart = 0
bricks, dud = 1 bricks
Data Table:
|
# of bricks exploder cart |
# of bricks dud cart |
Travel time (s) |
Distance of
exploder cart (in meters) |
Distance of dud cart (in meters) |
Ave. speed of
exploder (m/s) |
Ave. speed of dud
(m/s) |
|
|
|
|
|
|
|
|
Calculations:
Calculate the average
velocity of each cart.
Questions:
To be answered on a separate piece of paper as an individual for homework. Please use paragraph structure, complete sentences and observe the conventions of writing. This may be hand written or word-processed.