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 0.50 kg cart moves along a straight track; take the direction of increasing $x$ as positive. Its position is $x (t) = 2 t^{2} - 3 t$ , with $x$ in meters and $t$ in seconds. What is the cart's momentum at $t = 2$ s?

Your answer kg·m/s

Question 2 · from 4.2 · Calculate

A tennis racket hits a ball. The racket's force on the ball rises steadily from 0 to 400 N in 1.0 ms, stays at 400 N for 2.0 ms, then falls steadily back to 0 in 2.0 ms. Every other force on the ball is negligible during the hit. What is the size of the impulse the racket delivers to the ball?

Your answer N·s

Question 3 · from 4.3 · Sort it

Tap a card, then say what happens to the total momentum of the system it names.

Stays constant

Changes

Question 4 · from 4.4 · Spot the error

On a level track, take right as positive. A 0.40 kg cart moving right at 1.5 m/s hits a 0.60 kg cart at rest. During the 0.10 s of contact, the force on the 0.40 kg cart is $F (t) = - 3600 t (0.10 - t)$ , in newtons, with $t$ in seconds. A student classifies the collision. Tap the first line with a mistake.

Question 5 · from 4.1 · Multiple choice

On a level, frictionless air table, puck A (0.20 kg) slides east at 3.0 m/s and puck B (0.40 kg) slides north at 2.0 m/s. What is the size of the momentum of the two-puck system?

Question 6 · from 4.2 · Fill the statement

A 2.0 kg cart moves along a straight track. Its momentum is $p_{x} (t) = 12 t - 3 t^{2}$ , with $p_{x}$ in kg·m/s and $t$ in seconds. Take the direction of increasing $x$ as positive.

At $t = 3.0$ s, the net force on the cart is , and the cart's acceleration is .

Question 7 · from 4.3 · Calculate

A 5.0 kg toy rocket sled moves to the right at 2.0 m/s along a level track with negligible friction. A small charge splits it in two, and immediately afterward the 2.0 kg rear piece moves to the left at 3.0 m/s. Take right as positive. What is the velocity of the 3.0 kg front piece immediately after the split?

Your answer m/s

Setup for question 8

On paper. Take trial B from the ranking. Sketch the two carts just before and just after the collision, with a velocity arrow on every moving cart labeled with its value, and an arrow showing which way is positive. Then draw two energy bar charts for the system of both carts, one for just before and one for just after: a bar for kinetic energy and a bar for the other forms the missing kinetic energy became, with heights to scale. Check your bars against the energies in the ranking's feedback; the two charts should have the same total height.

Question 8 · from 4.4 · Rank it

Two 2.0 kg carts are on a level track. In each of three trials, one cart rolls east at 3.0 m/s into the other, which is at rest. Afterward, in trial A the first cart stops and the second moves east at 3.0 m/s. In trial B the carts stick together and move east at 1.5 m/s. In trial C the first cart moves east at 1.0 m/s and the second moves east at 2.0 m/s. Rank the trials by the kinetic energy transformed into other forms during the collision.

Greatest first

Give each one a place, 1 for first. Give two the same place if they are equal.

Trial A
Trial B
Trial C

Your ranking: none yet

Question 9 · from 4.1 · Sort it

Tap a card, then say which model fits the interaction it describes.

Collision

Explosion

Question 10 · from 4.2 · Calculate

Sand falls straight down onto a level conveyor belt at 15 kg/s. The belt moves at a constant 2.0 m/s. Take the belt and the sand on it as the system, and ignore friction in the rollers. What is the size of the horizontal net external force on the system?

Your answer N

0 of 10 answered.