Unit 5 Test

Question 1

Three pool balls of equal mass are resting on a horizontal frictionless surface. The cue ball (Ball 1) of mass 700 g is rolled into a stationary pool ball (Ball 2) and rebounds at 1.00 m / s in the direction from which it came. Ball 2 does not move, but it is touching another pool ball (Ball 3), which rolls away at 4.00 m / s. Which of the following is the initial speed of the cue ball, v1i? Also, given that the encounter between the cue ball and cue stick lasts for only 0.0500 s, which of the following is the average force delivered F to the cue ball by the stick?

Answer 1

v1i  = 3.00 m / s
F = 42.0 N

Question 2

Car 1 of mass 700 kg is slowly moving along at 0.500 m / s when it is hit from behind by car 2 speeding along at 15.0 m / s. After collision, car 1 has a new speed of 8.00 m / s in the same direction. Which of the following is the force with which car 2 must have struck car 1, if the collision lasted for 0.932 s? Also, knowing that conservation of momentum applies to the situation, what is car 2’s speed after the collision (v2 f ) if it has a mass of 850 kg?

Answer 2

F = 5.63 × 10^3 N
v2 f  = 8.82 m / s

Question 3

A 0.500 kg steel ball is dropped from a height of 4.00 m onto a horizontal steel slab. The collision appears elastic in that the ball rebounds to its original height. If the collision lasts for 2.00 × 10^−3 s, which of the following is the impulse imparted to the ball and the average force applied to the ball during the collision?

Answer 3

I = 8.85 kg•m / s
F = 4.43 × 10^3 N

Question 4

An empty freight train car of mass 10,000 kg is rolling along a level section of track at 2.00 m / s. It collides with a loaded car of weight 1.96 × 105 N, which is at rest. The cars couple upon collision. Which of the following is the speed of the train after the collision?

Answer 4

0.667 m / s

Question 5

A 1,450 kg car moves with a speed of 25.0 m / s when it collides with a stationary car having a mass of 1,550 kg. The two vehicles lock bumpers on impact. The two cars then collide with a stationary third car of mass 1,250 kg. During this second impact, the third vehicle becomes attached to the second but the first car is breaks free and moves at 0.125 m / s in the opposite direction. Which of the following is the final velocity of the second and third cars after the final collision?

Answer 5

13.01 m / s

Question 6

A spaceship is in space and currently at rest. The directive is given to accelerate from rest to a speed of 2.90 × 103 m / s. If the fuel budgeted for this action is 400 kg, which of the following is velocity of the exhaust gas required if the ship mass is 7.38 × 103 kg?

Answer 6

5.20 × 10^4 [m / s]

Question 7

Exhaust gas from a rocket ship is released at a speed of 1,000 m / s so that the craft accelerates from 100 m / s to 200 m / s. How much fuel is necessary to complete this acceleration if the mass of the ship was originally 10,000 kg?

Answer 7

951.6 kg

Question 8

Which of the following is the general definition of impulse ?

Answer 8

I = the integral from t1 to t2 sigma F dt

Question 9

A hammer head with a mass of 2 kg strikes a nail with a force of 50 N. If the contact lasts for 0.1 s, how fast was the hammer going at the moment of impact?

Answer 9

2.5 m / s

Question 10

A twelve-gauge shotgun fires a round of ammunition with a mass of 2 g and a velocity of 200 m / s. If it takes 0.01 s for the round to leave the gun, how much force will the shooter feel?

Answer 10

40 N

Question 11

A car equipped with airbags and crumple zones is moving at 30 m / s (108 mph) as it crashes into a brick wall. The 80 kg driver collides with the steering wheel for 0.5 s. How much force does the driver experience?

Answer 11

4,800 N

Question 12

A tennis ball with a mass of 0.5 kg and a velocity of 4 m / s is bounced off a wall at a 60° angle. How much force does it exert on the wall if its contact lasts 0.01 s?

Answer 12

346 N

Question 13

If an object in outer space is moving at a constant velocity and continues moving at that velocity forever, which of the following best describes the principle(s) at work?

Answer 13

Conservation of energy and momentum

Question 14

A pendulum with a bob of mass m is pulled up an initial height hi  and let go so the bob swings. At the bottom of the bob’s swing, it collides and sticks to an equal mass that is at rest. What is the maximum height hf  the combined mass is able to swing up to?

Answer 14

hi/4

Question 15

A glass ball is thrown straight down on concrete and breaks into four pieces that move away from each other horizontally. Using the information given in the diagram, which of the following is the speed of the largest piece?

Answer 15

1.5 m / s

Question 16

A rocket fires its engines for 2 s, which decreases the mass by 1%. The burned fuel is ejected with an exhaust speed of 2,000 m / s. Which of the following is the acceleration?

Answer 16

10 m / s2

Question 17

A rocket is fired in deep space and in the first second ejects 1/160 of it total mass as exhaust gas. If it has an acceleration of 15 m / s2, what is the speed of the exhaust gas relative to the rocket?

Answer 17

2,400 m / s

Question 18

A rocket is fired from rest in deep space. If all of its fuel is burned in 50 s, and the relative exhaust speed is 2,100 m / s, what must the mass ratio mo  /  mf  be for a final speed of 8,000 m / s?

Answer 18

45.2

Question 19

A truck weighing 1000 N moves at 5.89 m / s when it has an elastic collision with another vehicle. The second vehicle, weighing 981 N, was stationary but free to move. Which of the following is the final velocity of the first vehicle after the collision?

Answer 19

v1 f  = 0.0565 m / s

Question 20

A 309 g glass rolls down an incline and onto a horizontal platform where it hits a beverage can that is laying at rest on its side. The top of the incline is 11.0 cm above the horizontal platform. The beverage can is initially at rest and weighs 7.35 N. Which of following is the final speed of the glass?

Answer 20

−0.612 m / s

Question 21

In a game of marbles, a 60 g marble is rolling at 8.00 cm / s when it collides with a stationary marble. the 60 g marble takes off at a 27° angle at a reduced speed of 4.89 cm / s. The second marble moves at a rate of 3.21 cm / s at a 31.7° angle. Which of the following is the mass of the second marble?

Answer 21

0.0800 kg

Question 22

A 0.200 kg dart is fired horizontally at a speed of 2.75 m / s when it hits a 0.700 kg block of wood suspended by a string. The nose of the dart sticks into 0.00210 m the wood. Together the dart and block swing upwards from a height of 0.0500 m above a table to 0.128 m above the table. Which of the following is the average force the dart applies to the block during impact?

Answer 22

32.4 N

Question 23

A surveillance plane weighing 1.91 × 104 N is flying horizontally at a velocity of 59.4 m / s due west in thick clouds. Suddenly the plane is struck a glancing blow from another plane. Before impact, this smaller plane weighing 9.74 × 103 N was traveling at 114 m / s due northwest at constant altitude. Immediately after impact, the second plane is knocked of course to a heading of 89.8 m / s at 35.2° north of west. Which of the following is the velocity of the surveillance plane after the collision?

Answer 23

64.8 m / s at 13.1° north of west

Question 24

Consider an isolated system consisting of two objects. In an elastic collision between the two objects, which of the following statements is incorrect?

Answer 24

The kinetic energy of each object remains unchanged during the collision.

Question 25

A 50 kg boy runs at a speed of 6.0 m / s and jumps into a cart, which was at rest on a frictionless surface. If the speed of the cart with the boy in it is 2.0 m / s, which of the following is the mass of the cart?

Answer 25

100 kg