WorksheetsReview Unit 6 Momentum
Total questions: 9
Worksheet time: 17mins
The graph above shows the position x as a function of time for the center of mass of a system of particles of total mass 6.0 kg. For a very short time interval around 2.0 s, an external force is exerted on an object in the system. What is the resulting change in momentum of the system?
-18 Kg.m/s
-6 Kg.m/s
6 Kg.m/s
52 Kg.m/s
Which of the following is true of the motion of the center of mass of the two-block system during the time shown?
The center of mass moves at a constant velocity of +1.0 m/s because there is no friction acting on the system.
The center of mass does not move because the blocks are moving in opposite directions before the collision.
The center-of-mass velocity increases as the blocks get closer together, and then becomes constant after the collision.
The center-of-mass velocity starts out greater than +1.0 m/s but decreases to +1.0 m/s during the collision because the collision is inelastic.
The two blocks of masses M and 2M shown above initially travel at the same speed v but in opposite directions. They collide and stick together. How much mechanical energy is lost to other forms of energy during the collision?
3/2Mv2
4/3Mv2
Zero
1/2Mv2
How does an air bag protect a driver in a crash?
It reduces the momentum change of the driver.
It reduces the kinetic energy loss of the driver.
It increases the momentum change of the driver.
It shortens the stopping time of the driver and increases the force applied during the landing.
It lengthens the stopping time of the driver and reduces the force applied during the landing.
A brother and sister are standing next to each other at rest on surface of frictionless ice. The brother’s mass is exactly twice that of his sister’s. The sister suddenly pushes her brother. As a result, the sister moves with kinetic energy K. What is the resulting kinetic energy of the brother?
4K
K/2
2K
K/4
How does the kinetic energy of the two-block system after the collision compare with its kinetic energy before the collision, and why?
It is less, because the blocks have the same velocity after the collision, so some of their kinetic energy was transformed into internal energy.
It is less, because the blocks have velocities in opposite directions before the collision, so some of their kinetic energy cancels.
It is the same, because the collision was instantaneous, so the effect of external forces during the collision is negligible.
It is the same, because the blocks have the same velocity after the collision, and there is no friction acting on them.
A stationary cart attached to a force gauge is on a straight, horizontal, frictionless track. A student uses the force gauge to move the cart, and the gauge produces the graph of force as a function of time shown above. How does the momentum of the cart change during the time interval 0 s to 20 s?
The momentum decreases in magnitude during the entire time interval.
The momentum increases in magnitude at first, then decreases without reversing direction.
The momentum increases in magnitude at first, then decreases and reverses direction.
The momentum increases in magnitude during the entire time interval.
A projectile fired into the air explodes and splits into two halves of equal mass that hit the ground at the same time. If the projectile had not exploded, it would have landed at point X, which is a distance R to the right of the launch point. After the explosion, one of the halves lands at point Y, which is a distance 2R to the right of the launch point. If air resistance is negligible, where did the other half land?
Between points X and Y
Between the launch point and point, X
At the launch point
To the left of the launch point
A spacecraft of mass 4000 kg is traveling in a straight line in the positive direction. Engines can be fired so that the force exerted on the spacecraft is in the positive or negative direction. The graph above shows data for the force during one interval. Which of the following is the best estimate of the net change in the speed of the spacecraft from time t = 0 to time t = 4 s?
+ 0.4 m/s
+ 0.1 m/s
- 0.4 m/s
- 0.1 m/s
