Chap 9 Test Review

A freight car with a mass of 10 metric tons is rolling at 108 km/h along a level track when it collides with another freight car, which is initially at rest. If the speed of the cars after they couple together is 36 km/h, what is the mass of the second car?

• 5 metric tons

• 40 metric tons

• 20 metric tons

• 10 metric tons

A rocket leaves a launch pad at liftoff with a great deal of upward momentum. What was initially given downward momentum?

• the launch pad

• the astronauts aboard the rocket

• the expelled fuel

• the entire Earth

Which conditions will result in the smallest change in momentum?

• a large force over a long time period

• a large force over a short time period

• a small force over a long time period

• a small force over a short time period

Aisha is sitting on frictionless ice and holding two heavy ski boots. Aisha weighs 637 N, and each boot has a mass of 4.50 kg. Aisha throws both boots forward at the same time, at a velocity of 6.00 m/s relative to her. What is Aisha’s resulting velocity?

• 0.831 m/s

• 1.45 m/s

• 54 m/s

• 0.54 m/s

At 9.0 s after takeoff, a 250-kg rocket attains a vertical velocity of 120 m/s.

What is the average force on the rocket?

• 3.4 x 10V4 N

• 3300 N

• 3.0131 N

• 4552 N

A 10.0-g bullet is fired into a stationary 5.00-kg block of wood. The bullet lodges inside the block. The speed of the block-plus-bullet system immediately after the collision is measured as 0.600 m/s. What was the original speed of the bullet?

• 0.9 m/s

• 301 m/s

• 0.306 m/s

• 127.5 m/s

In a circus act, a 18-kg dog is trained to jump onto a 3.0-kg skateboard moving with a velocity of 0.14 m/s. At what velocity does the dog jump onto the skateboard if afterward the velocity of the dog and skateboard is –0.10 m/s?

• 14.1 m/s

• 1.14 m/s

• 0.442 m/s

• 0.14 m/s

A tennis player receives a shot with the 60.0-g ball traveling horizontally at –50.0 m/s, and returns the shot with the ball traveling horizontally. The tennis ball and the tennis racket are in contact for 1.00×10^–3 s. The average force exerted on the ball by the tennis racket is 5.70×10³ N. Find the speed of the tennis ball after it leaves the racket.

• 14.5 m/s

• 40.5 m/s

• 126.5 m/s

• 24.6 m/s

A 2.0 kg bird lands on a 1.0 10¹ kg bit of tree bark sitting on a frictionless ice-covered pond. The bird’s initial horizontal speed is 6.0 m/s. What is the final speed of the bird and bark?

• 2.0 m/s

• 1.0 m/s

• 0.1 m/s

• 0.2 m/s

Analyze the collision of a baseball with a bat. During which portion of the collision does the baseball’s velocity reach zero?

• before the collision

• during the collision

• one second after the collision

• one-hundredth of a second after the collision