Unit 4 check
Unit 4 check: Linear Momentum
10 questions from 4 lessons in Unit 4. Answer each one, and if you miss, follow the link back to where it is taught, then try again. Your score counts first tries.
Question 1 · from 4.1 · Calculate
A 55 kg skateboarder, board included, rolls along a level path at 4.0 m/s. What is the magnitude of the skateboarder's momentum? Give your answer to the nearest kg·m/s.
Question 2 · from 4.2 · Decide and justify
In a crash test, a dummy moving forward at 15 m/s is brought to rest. In one run only the steering wheel stops it. In another run only an airbag stops it, over a much longer time. Does the airbag deliver a smaller impulse to the dummy than the steering wheel does?
Which reason supports your answer?
Question 3 · from 4.3 · Sort it
Each card describes an event and names a system. Tap a card, then what happens to that system's total momentum during the event.
Stays constant
Changes
Setup for question 4
A lab partner measured only one glider before and after an elastic collision, and you want the energy the other glider carried away. In an elastic collision the total kinetic energy is fixed, so what one glider gives up, the other gains.
Question 4 · from 4.4 · Calculate
On a level air track, with right as positive, a 0.30 kg glider moving right at 5.0 m/s collides elastically with a 0.20 kg glider at rest. Just after the collision, the 0.30 kg glider moves right at 1.0 m/s. How much kinetic energy does the 0.20 kg glider have just after the collision? Give your answer to the nearest 0.01 J.
Question 5 · from 4.1 · Decide and justify
Two identical 1.2 kg carts roll toward each other on a level track, each at 1.5 m/s. Take right as positive. A student says the total momentum of the two-cart system is 3.6 kg·m/s, since each cart has 1.8 kg·m/s. Is the student right?
Which reason supports your answer?
Question 6 · from 4.2 · Sketch the graph
A 1.5 kg cart rolls to the right at 4.0 m/s along a level track, with right as positive. A graph of the net force on the cart against time reads 0 from 0 to 2 s, a steady -2.0 N from 2 s to 5 s, and 0 again from 5 s to 6 s. Sketch the cart's momentum against time from 0 to 6 s. The first point is fixed at the cart's momentum at 0 s.
One shape that fits
Drag a point up or down, or tap it and use the arrow keys. The shape is checked, and the graph must pass through the values the question gives.
Question 7 · from 4.3 · Multiple choice
On a level air table, where friction is negligible, puck A of mass 0.30 kg slides east at 2.0 m/s and hits puck B of mass 0.30 kg, which is at rest. Just after the collision, puck A moves east and north, with an eastward part slower than 2.0 m/s. Take east and north as positive. Which describes puck B's velocity just after the collision?
Setup for question 8
A student runs four collisions on a level track, where the carts' wheels roll freely. In every trial, cart 1 (mass 2.00 kg) moves at m/s toward cart 2, which is at rest, with right as positive. Between trials she changes cart 2's mass and the bumpers on both carts. Motion sensors record each cart's velocity just after the collision.
| Trial | Mass of cart 2 (kg) | Cart 1 after (m/s) | Cart 2 after (m/s) |
|---|---|---|---|
| 1 | 4.00 | -0.20 | +1.00 |
| 2 | 1.60 | +1.00 | +1.00 |
| 3 | 1.00 | +0.72 | +2.16 |
| 4 | 2.80 | -0.30 | +1.50 |
Question 8 · from 4.4 · Multiple choice
Using the collision table, in which trial was the collision elastic?
Question 9 · from 4.1 · Sort it
Each card describes a brief interaction between objects. Tap a card, then the model that fits it.
Collision model
Explosion model
Question 10 · from 4.2 · Fill the statement
Tap a blank, then an answer.
The net external force on a system equals the rate at which the system's changes. If no material enters or leaves the system, its stays constant, and that rate becomes the mass times the , which is Newton's second law.
0 of 10 answered.