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# momentum and impulse

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1. A stunt person jumps from the roof of a tall building, but no injury occurs because the person lands on a large, air-filled bag. Which one of the following best describes why no injury occurs?

2. Jennifer is walking at 1.63 m/s. If Jennifer weighs 583 N, what is the magnitude of her momentum?

3. A 1.0-kg ball has a velocity of 12 m/s downward just before it strikes the ground and bounces up with a velocity of 12 m/s upwards. What is the change in momentum of the ball?

4. A 0.1-kg steel ball is dropped straight down onto a hard horizontal floor and bounces straight up. Its speed just before and just after impact with the floor is 10 m/s. Determine the magnitude of the impulse delivered to the floor by the steel ball.

5. A machine gun fires 50-g bullets at the rate of 4 bullets per second. The bullets leave the gun at a speed of 1000 m/s. What is the average recoil force experienced by the machine gun?

6. While a car is stopped at a traffic light in a storm, raindrops strike the roof of the car. The area of the roof is 5.0 m2. Each raindrop has a mass of 3.7 9 10^-4 kg and speed of 2.5 m/s before impact and is at rest after impact. If, on average at a given time, 150 raindrops strike each square meter, what is the impulse of the rain striking the car?

7. A bat strikes a 0.050-kg baseball so that its velocity changes by +30 m/s in 0.10 s. With what average force was the ball struck?

8. A 100-kg cannon at rest contains a 10-kg cannon ball. When fired, the cannon ball leaves the cannon with a speed of 90 m/s. What is the recoil speed of the cannon?

9. An 80-kg astronaut carrying a 20-kg tool kit is initially drifting toward a stationary space shuttle at a speed of 2 m/s. If she throws the tool kit toward the shuttle with a speed of 6 m/s as seen from the shuttle, her final speed is

10. Two cars of equal mass collide on a horizontal frictionless surface. Before the collision, car A is at rest while car B has a constant velocity of 12 m/s. After the collision, the two bodies are stuck together. What is the speed of the composite body after the collision.

https://brainmass.com/physics/velocity/momentum-impulse-174898

## SOLUTION This solution is FREE courtesy of BrainMass!

1. E
2.

3. Assume upward direction is positive.
The initial velocity vi = - 12 m/s, the negative sign indicates its direction is downward.
The final velocity vf = 12 m/s.
Change in momentum is

4. By impulse-momentum theorem,

5. By impulse-momentum theorem,
The time of the bullet in the gun is 1 seconds / 4 = 0.25 second since the gun fires 4 bullets in 1 second.

6. For each raindrop,

In the area of 5.0 m2, there are 5 * 150 = 750 raindrops.
So the total impulse striking the car is
750 * = 0.69 N• s.

7.

8. The initial momentum of the cannon and the cannon ball is 0. then
Based on the conservation of momentum:

9. The initial momentum of the two together is (m + mk)vi, where m is the mass of the astronaut, mk is the mass of the tool kit, vi = 2 m/s. and we assumed the direction toward the space shuttle is positive.
After the tool is thrown out, its momentum is mkvk, where vk = 6 m/s.
Based on the conservation of momentum:

So the velocity of the astronaut is 1 m/s toward the shuttle.