Deck 7: Linear Momentum

Question 1

A 1200 kg car is traveling at 3.0 m/s and strikes a wall. The car bounces off the wall with a velocity of 4.0 m/s in the opposite direction. If the car is in contact with the wall for 0.10 seconds, then the magnitude of the average force of the wall on the car is

A) 46,000 N.
B) 55,000 N.
C) 63,000 N.
D) 75,000 N.
E) 84,000 N.

Answer 1

84,000 N.

Question 2

A machine gun fires 60.0 gram bullets at a rate of 6 bullets per second. If the speed of the bullets is 600 m/s, then the magnitude of the average recoil force on the machine gun is

A) 67.0 N.
B) 75.0 N.
C) 94.0 N.
D) 109 N.
E) 216 N.

Answer 2

216 N.

Question 3

A model rocket with a mass of 750 grams is launched straight up. It achieves a speed of 25.0 m/s in 2.00 seconds. Ignoring any change in mass of the rocket due to expelled fuel, and neglecting air resistance, the magnitude of the average net force on the rocket is

A) 9.38 N.
B) 24.5 N.
C) 16.7 N.
D) 41.7 N.
E) 52.8 N.

Answer 3

9.38 N.

Question 4

A 1200 kg car is traveling at 4.00 m/s and strikes a wall. The car bounces off the wall with a velocity of 4.00 m/s in the opposite direction. If the car is in contact with the wall for 0.100 seconds, then the magnitude of the impulse on the car is

A) 12,400 kg m/s.
B) 10,200 kg m/s.
C) 9,600 kg m/s.
D) 8,400 kg m/s.
E) 2,900 kg m/s.

Question 5

An 1800 kg car traveling at 35.0 m/s strikes a wall. If the car comes to rest in 0.500 seconds, then the magnitude of the average force of the wall on the car is

A) 0.330 × 10⁵ N.
B) 0.640 × 10⁵ N.
C) 1.26 × 10⁵ N.
D) 2.77 × 10⁵ N.
E) 3.33 × 10⁵ N.

Question 6

A 140 g baseball with a velocity of 25.0 m/s is hit by a baseball bat and leaves at 30.0 m/s in the opposite direction. If the ball was in contact with the bat for 12.0 ms, what was the average force on the ball?

A) 750 N
B) 642 N
C) 550 N
D) 482 N
E) 366 N

Question 7

A water hose has a flow rate of 3.0 kg/s of water. If the speed of the water as it leaves the hose is 5.0 m/s, then the magnitude of the additional force required to hold the hose as a result of the water being expelled is

A) 15 N.
B) 26 N.
C) 30 N.
D) 45 N.
E) 57 N.

Question 8

A 30.00 kg mass falls from a height of 2.000 m. The magnitude of the momentum of the mass just before it hits the ground is

A) 144.2 kg m/s.
B) 187.8 kg m/s.
C) 320.0 kg m/s.
D) 442.4 kg m/s.
E) 502.1 kg m/s.

Question 9

A 5.0 kg ball is traveling at 4.0 m/s and strikes a wall. The ball bounces off the wall with a velocity of 4.0 m/s in the opposite direction. If the ball is in contact with the wall for 0.10 seconds, then the magnitude of the impulse on the ball is

A) 24 kg m/s.
B) 30 kg m/s.
C) 36 kg m/s.
D) 40 kg m/s.
E) 50 kg m/s.

Question 10

A model rocket with a mass of 500 grams is launched straight up. It achieves a speed of 20.0 m/s in 2.00 seconds. Ignoring any change in mass of the rocket due to expelled fuel, and neglecting air resistance, the average thrust force of the engines on the rocket is

A) 7.50 N.
B) 9.90 N.
C) 12.0 N.
D) 13.5 N.
E) 20.0 N

Question 11

A rifle fires a bullet. Immediately after the bullet is fired, which of the following is not true?

A) The rifle and the bullet have the same magnitude of momentum.
B) The force on the rifle due to the bullet and the force on the bullet due to the rifle have the same magnitude.
C) The impulse on the rifle due to the bullet and the impulse on the bullet due to the rifle have the same magnitude.
D) The rifle and the bullet have the same kinetic energy.

Question 12

A 3.000 kg ball is pitched with a kinetic energy of 20.00 J. The magnitude of the momentum of the ball is

A) 7.500 kg m/s.
B) 8.350 kg m/s.
C) 9.450 kg m/s.
D) 10.95 kg m/s.
E) 12.50 kg m/s.

Question 13

If the momentum of a ball is doubled, then the kinetic energy is

A) 0.5 times larger.
B) 2 times larger.
C) 3 times larger.
D) 4 times larger.
E) 5 times larger.

Question 14

A 4.0 kg ball is traveling at 3.0 m/s and strikes a wall. The ball bounces off the wall with a velocity of 4.0 m/s in the opposite direction. If the ball is in contact with the wall for 0.10 seconds, then the magnitude of the average force on the ball during contact is

A) 230 N.
B) 280 N.
C) 320 N.
D) 360 N.
E) 400 N.

Question 15

The units of momentum are

A) ML/T.
B) M/T.
C) L/T².
D) ML/T².
E) ML²/T².

Question 16

If the kinetic energy of a ball is doubled, then the momentum is about

A) 0.50 times larger.
B) 0.71 times larger.
C) 1.00 times larger.
D) 1.41 times larger.
E) 1.50 times larger.

Question 17

A 2.0 kg ball is moving at 4.0 m/s WEST. The momentum of the ball is

A) 4.00 kg m/s WEST.
B) 6.00 kg m/s WEST.
C) 8.0 kg m/s WEST.
D) 10 kg m/s WEST.
E) 12 kg m/s WEST.

Question 18

A 4.0 kg ball is traveling at 5.0 m/s to the right and strikes a wall. The ball bounces off the wall with a velocity of 4.0 m/s to the left. The change in momentum of the ball is

A) 4.0 kg m/s left.
B) 36 kg m/s right.
C) 26 kg m/s left.
D) 30 kg m/s right.
E) 36 kg m/s left.

Question 19

Two objects of equal mass and velocity hit a wall. They both rebound with the same velocity in the opposite direction. Both objects experience the same momentum change but one experiences twice the average force as the other. Which of the following statements is true?

A) The contact time between one of the objects and the wall is twice the contact time of the other.
B) The contact times between the objects and the wall are equal.
C) The contact time between one of the object and the wall is one-fourth the contact time of the other.
D) The change in the kinetic energy is different for the two objects.
E) The contact time between one of the objects and the wall is 1/3 the contact time of the other.

Question 20

A 1,800 kg car is traveling at 20.0 m/s NORTHEAST. The momentum of the car is

A) 18,000 kg m/s NORTHEAST.
B) 20,000 kg m/s NORTHEAST.
C) 28,000 kg m/s NORTHEAST.
D) 32,000 kg m/s NORTHEAST.
E) 36,000 kg m/s NORTHEAST.

Question 21

A 4.00 kg ball is moving at 4.00 m/s to the EAST and a 6.00 kg ball is moving at 3.00 m/s to the NORTH. The total momentum of the system is

A) 14.2 kg m/s at an angle of 48.4 degrees SOUTH of EAST.
B) 48.2 kg m/s at an angle of 24.2 degrees SOUTH of EAST.
C) 48.2 kg m/s at an angle of 48.4 degrees NORTH of EAST.
D) 24.1 kg m/s at an angle of 24.2 degrees SOUTH of EAST.
E) 24.1 kg m/s at an angle of 48.4 degrees NORTH of EAST.

Question 22

A 120 kg mass, initially at rest, is blown apart into an 80 kg piece and a 40 kg piece. After the blast, the two masses are moving apart with a relative velocity of 60 m/s. The total kinetic energy after the explosion is

A) 21 kJ.
B) 35 kJ.
C) 48 kJ.
D) 56 kJ.
E) 82 kJ.

Question 23

An astronaut in a space suit is motionless in outer space. The propulsion unit strapped to her back ejects some gas with a velocity of magnitude 40.0 m/s. The astronaut recoils with a velocity of 1.00 m/s in the opposite direction. If the mass of the astronaut and space suit after the gas is ejected is 100 kg and the mass of the gas ejected is 2.50 kg, then the total kinetic energy is

A) 2,050 J.
B) 3,430 J.
C) 4,150 J.
D) 5,070 J.
E) 6,320 J.

Question 24

Two ice skaters are at rest and facing each other. One skater weighs 140 lbs and the other skater weighs 180 lbs. The skaters "push off" of each other. The 140 lb skater then moves away at 5.00 m/s to the EAST. What is the velocity of the 180 lb skater?

A) 6.50 m/s EAST
B) 6.50 m/s WEST
C) 3.89 m/s EAST
D) 3.89 m/s WEST
E) 1.55 m/s EAST

Question 25

A 4.00 kg ball is moving at 2.00 m/s to the WEST and a 6.00 kg ball is moving at 2.00 m/s to the NORTH. The total momentum of the system is

A) 21.6 kg m/s at an angle of 17.7 degrees NORTH of WEST.
B) 14.4 kg m/s at an angle of 45.2 degrees SOUTH of WEST.
C) 21.6 kg m/s at an angle of 45.2 degrees SOUTH of WEST.
D) 14.4 kg m/s at an angle of 56.3 degrees NORTH of WEST.
E) 21.6 kg m/s at an angle of 56.3 degrees NORTH of WEST.

Question 26

An airplane has a mass of 8,000 kg and is flying at 150 m/s in level flight. The airplane drops 1,000 kg of water on a fire below. The speed of the airplane after dropping the water is

A) 50 m/s.
B) 60 m/s.
C) 75 m/s.
D) 100 m/s.
E) 150 m/s.

Question 27

A 4.00 kg ball is moving at 4.0 m/s to the right and a 6.00 kg ball is moving at 3.00 m/s to the left. The total momentum of the system is

A) 16 kg m/s to the right.
B) 2.0 kg m/s to the right.
C) 2.0 kg m/s to the left.
D) 18 kg m/s to the left.
E) 34 kg m/s to the left.

Question 28

A 100.0 kg mass is blown apart into a 95.00 kg piece and a 5.000 kg piece. After the blast, the two masses are moving apart with a relative velocity of 100.0 m/s. The kinetic energy of the 95.00 kg mass after the explosion is

A) 1,190 J.
B) 8,600 J.
C) 18,750 J.
D) 22,560 J.
E) 23,750 J.

Question 29

A 100 kg mass, initially at rest, is blown apart into two 50.0 kg pieces. After the blast, the two masses are moving apart with a relative velocity of 100 m/s. The total kinetic energy after the explosion is

A) 8.42 × 10⁴ J.
B) 1.25 × 10⁵ J.
C) 3.62 × 10⁵ J.
D) 6.50 × 10⁵ J.
E) 1.24 × 10⁶ J.

Question 30

A 4.00 kg ball is moving at 3.00 m/s to the NORTH and a 5.00 kg ball is moving at 2.00 m/s to the NORTHEAST. The total momentum of the system is

A) 20.3 kg m/s at an angle of 69.7 degrees NORTH of EAST.
B) 20.3 kg m/s at an angle of 24.6 degrees SOUTH of EAST.
C) 26.1 kg m/s at an angle of 24.6 degrees NORTH of EAST.
D) 26.1 kg m/s at an angle of 69.7 degrees SOUTH of EAST.
E) 43.00 kg m/s at an angle of 45.0 degrees NORTH of EAST.

Question 31

A 4.00 kg ball is moving at 2.00 m/s to the SOUTH and a 6.00 kg ball is moving at 2.00 m/s to the NORTHWEST. The total momentum of the system is

A) 15.8 kg m/s at an angle of 3.27 degrees NORTH of WEST.
B) 8.5 kg m/s at an angle of 3.27 degrees NORTH of WEST.
C) 15.8 kg m/s at an angle of 17.2 degrees NORTH of WEST.
D) 8.5 kg m/s at an angle of 17.2 degrees NORTH of WEST.
E) 20.1 kg m/s at an angle of 27.5 degrees NORTH of WEST.

Question 32

A 120 kg mass, initially at rest, is blown apart into a 80 kg piece and a 40 kg piece. After the blast, the two masses are moving apart with a relative velocity of 60 m/s. The speed of the 80 kg mass is

A) 59 m/s.
B) 51 m/s.
C) 34 m/s.
D) 20 m/s.
E) 14 m/s.

Question 33

A 5.00 kg ball is moving at 4.0 m/s to the right and a 6.00 kg ball is moving at 3.00 m/s to the left. The total momentum of the system is

A) 2.0 kg m/s to the right.
B) 2.0 kg m/s to the left.
C) 38 kg m/s to the right.
D) 18 kg m/s to the left.
E) 20 kg m/s to the right.

Question 34

A 100 kg mass, initially at rest, is blown apart into a 60 kg piece and a 40 kg piece. After the blast, the two masses are moving apart with a relative velocity of 60 m/s. The speed of the 60 kg mass is

A) 88 m/s.
B) 67 m/s.
C) 51 m/s.
D) 40 m/s.
E) 24 m/s.

Question 35

A 100.0 kg mass, initially at rest, is blown apart into a 95.00 kg piece and a 5.000 kg piece. After the blast, the two masses are moving apart with a relative velocity of 100.0 m/s. The kinetic energy of the 5.000 kg mass after the explosion is

A) 6,850 J.
B) 7,500 J.
C) 9,570 J.
D) 11,500 J.
E) 22,560 J.

Question 36

A 3.0 kg object is moving to the right at 4.0 m/s. It collides in a perfectly inelastic collision with a 6.0 kg object moving to the left at 2.0 m/s. What is the total kinetic energy after the collision?

A) 62 J
B) 25 J
C) 12 J
D) 0.0 J

Question 37

A 90.0 kg person is sitting in a 100 kg boat, which is floating at rest on a lake. In the boat is a stone with a mass of 5.00 kg. The person throws the stone at 4.00 m/s horizontally in the NORTH direction. The kinetic energy of the boat and person after throwing the stone is

A) 5.20 J.
B) 40.0 J.
C) 1.05 J.
D) 2.75 J.

Question 38

An astronaut in a space suit is motionless in outer space. The propulsion unit strapped to her back ejects some gas with a velocity of magnitude 50 m/s. The astronaut recoils with a velocity of 1.0 m/s in the opposite direction. If the mass of the astronaut and space suit after the gas is ejected is 120 kg, the mass of the gas ejected is

A) 1.0 kg.
B) 1.9 kg.
C) 2.4 kg.
D) 3.0 kg.
E) 3.6 kg.

Question 39

A 100 kg mass, initially at rest, is blown apart into a 90.0 kg piece and a 10.0 kg piece. After the blast, the two masses are moving apart with a relative velocity of 100 m/s. The speed of the 10.0 kg mass after the explosion is 90.0 m/s. The total kinetic energy of the two masses after the explosion is

A) 63,200 J.
B) 45,000 J.
C) 30,400 J.
D) 23,400 J.
E) 4,500 J.

Question 40

A 90 kg person is sitting in a 100 kg boat, which is floating at rest on a lake. In the boat is a stone with a mass of 5.0 kg. The person throws the stone at 4.0 m/s horizontally in the NORTH direction. The velocity of the person and the boat after throwing the stone is

A) 2.00 m/s NORTH.
B) 1.21 m/s SOUTH.
C) 1.21 m/s NORTH.
D) 0.11 m/s SOUTH.
E) 0.11 m/s NORTH.

Question 41

A 3.00 kg mass is located at x = 2.0 cm and y = 4.0 cm. A 3.00 kg mass is located at x = −5.0 cm and y = 2.0 cm. A 4.00 kg mass is located at x = 3.0 cm and y = −3.0 cm. Where is the center of mass (x, y)?

A) (0.60 cm, 0.30 cm)
B) (0.90 cm, 2.0 cm)
C) (3.0 cm, 1.0 cm)
D) (0.30 cm, 0.60 cm)
E) (3.9 cm, 3.0 cm)

Question 42

A 3.00 kg mass is located at x = 2.0 cm and y = 0.0 cm. A 3.00 kg mass is located at x = 0.0 cm and y = 2.0 cm. A 4.00 kg mass is located at x = 3.0 cm and y = −3.0 cm. Where is the location of the center of mass?

A) (1.8 cm, −0.60 cm)
B) (1.8 cm, 0.60 cm)
C) (0.60 cm, −1.8 cm)
D) (3.5 cm, −0.6 cm)
E) (1.8 cm, 1.6 cm)

Question 43

A 3.00 kg mass is located at x = 2.0 cm and y = −4.0 cm. A 3.00 kg mass is located at x = −5.0 cm and y = 2.0 cm. A 4.00 kg mass is located at x = −3.0 cm and y = −3.0 cm. Where is the center of mass (x, y)?

A) (−0.10 cm, −0.50 cm)
B) (−2.1 cm, −1.8 cm)
C) (+2.1 cm, −1.8 cm)
D) (−2.1 cm, +1.8 cm)
E) (+1.1 cm, −2.0 cm)

Question 44

A 5.00 kg mass is moving at 4.00 m/s 30.0 degrees SOUTH of WEST and a 2.00 kg mass is moving at 3.00 m/s 60.0 degrees SOUTH of EAST. Find the velocity of the center of mass, letting (a) = the east-west component, and (b) = the north-south component.

A) a = +2.17 m/s, b = −2.05 m/s.
B) a = −2.17 m/s, b = +2.05 m/s.
C) a = +2.05 m/s, b = −2.17 m/s.
D) a = −2.05 m/s, b = +2.17 m/s.
E) a = −2.05 m/s, b = −2.17 m/s.

Question 45

An open boxcar has a mass of 30,000 kg and is moving on a level railroad track at 4.00 m/s. 1,000 kg of water falls straight down into the boxcar. The speed of the boxcar after the water falls into it is

A) 7.01 m/s.
B) 6.55 m/s.
C) 5.02 m/s.
D) 3.87 m/s.
E) 2.89 m/s.

Question 46

A 4.00 kg object is moving at 3.00 m/s WEST. It catches up to and strikes a 6.00 kg that is moving WEST at 2.00 m/s. The objects undergo an elastic collision in the EAST-WEST direction. The velocity of the 4.00 kg object after the collision is

A) 1.00 m/s WEST.
B) 2.80 m/s EAST.
C) 1.80 m/s WEST.
D) 2.80 m/s WEST.
E) 1.80 m/s EAST.

Question 47

A 4.00 kg object is moving at 5.00 m/s EAST. It strikes a 5.00 kg that is moving WEST at 2.00 m/s. The objects collide elastically and move away in the EAST-WEST direction. The velocity of the 5.00 kg object after the collision is

A) 4.22 m/s EAST.
B) 2.78 m/s WEST.
C) 4.22 m/s WEST.
D) 2.78 m/s EAST.
E) 1.11 m/s WEST.

Question 48

If a 5.00 kg mass is moving EAST at 10.0 m/s and a 15.0 kg mass is moving WEST at 10 m/s, what is the velocity of the center of mass of the pair?

A) 10 m/s WEST
B) 5.0 m/s EAST
C) 5.0 m/s WEST
D) 10 m/s EAST

Question 49

A 4.00 kg mass is moving at 4.00 m/s 45.0 degrees NORTH of WEST and a 6.00 kg mass is moving at 3.00 m/s 30.0 degrees SOUTH of EAST. Find the velocity of the center of mass, letting (a) = the east-west component, and (b) = the north-south component.

A) a = 0.427 m/s, b = 2.31 m/s.
B) a = 1.23 m/s, b = 0.231 m/s.
C) a = 0.427 m/s, b = 0.231 m/s.
D) a = 1.73 m/s, b = 1.43 m/s.
E) a = 0.427 m/s, b = 0.213 m/s.

Question 50

A 30.0 g mass is located at the origin. Where must a mass of 10.0 g be located if the coordinates of the center of mass are (0.00 cm, 10.0 cm)?

A) (0.00 cm, 5.00 cm)
B) (0.00 cm, 7.50 cm)
C) (0.00 cm, 10.0 cm)
D) (0.00 cm, 20.0 cm)
E) (0.00 cm, 40.0 cm)

Question 51

Two objects collide and stick together. Which of the following is false?

A) momentum is conserved
B) kinetic energy is lost
C) kinetic energy is conserved
D) total energy is conserved
E) the collision is perfectly inelastic

Question 52

A 10 kg bomb is moving NORTH with a velocity of 4.0 m/s. It explodes into three fragments: a 5.0 kg fragment moving WEST with a speed of 8.0 m/s, a 4.0 kg fragment moving EAST with a speed of 10 m/s, and a third 1.0 kg fragment. What is the velocity of the third fragment?

A) zero
B) 40 m/s NORTH
C) 40 m/s SOUTH
D) none of these answers are correct

Question 53

A 4.0 kg object is moving at 5.0 m/s NORTH. It strikes a 6.0 kg object at rest. The objects collide elastically and move away in the NORTH or SOUTH direction. The velocity of the 6.0 kg object after the collision is

A) 0.0 m/s.
B) 1.0 m/s SOUTH.
C) 4.0 m/s SOUTH.
D) 1.0 m/s NORTH.
E) 4.0 m/s NORTH.

Question 54

A rocket of length 80 m sits on a launch pad in outer space. The center of mass of the combined rocket and launch pad system is located in the center of the launch pad. The rocket is launched and reaches a distance of 100,000 km from the starting position. Where is the location of the center of mass of the total rocket-fuel-launch pad system then?

A) at the center of the launch pad
B) at the starting position
C) 100,000 km from the launch pad
D) 80 m from the launch pad
E) 50,000 km from the launch pad

Question 55

A 3.00 kg mass and a 4.00 kg mass are dropped from a great height simultaneously. What is the magnitude of the velocity of the center of mass at t = 10 s (ignore air resistance)?

A) 9.8 m/s
B) 7.0 m/s
C) 70 m/s
D) 98 m/s

Question 56

A 3.00 kg object is moving at 5.00 m/s EAST. It catches up to and strikes a 6.00 kg that is moving EAST at 2.00 m/s. The objects undergo an elastic collision in the EAST-WEST direction. The velocity of the 3.00 kg object after the collision is

A) 4.00 m/s EAST.
B) 1.00 m/s EAST.
C) 4.00 m/s WEST.
D) 1.00 m/s WEST.
E) 3.00 m/s EAST.

Question 57

A 4.0 kg object is moving at 5.0 m/s NORTH. It strikes a 6.0 kg object at rest. The objects collide elastically and move away in the NORTH or SOUTH direction. The velocity of the 4.0 kg object after the collision is

A) 1.0 m/s NORTH.
B) 4.0 m/s NORTH.
C) 1.0 m/s SOUTH.
D) 4.0 m/s SOUTH.
E) 0 m/s.

Question 58

A 4.00 kg object is moving at 5.00 m/s WEST. It catches up to and strikes a 6.00 kg that is moving WEST at 2.00 m/s. The objects undergo an elastic collision and move away in the EAST-WEST direction. The velocity of the 6.00 kg object after the collision is

A) 1.40 m/s WEST.
B) 1.40 m/s EAST.
C) 4.40 m/s EAST.
D) 4.40 m/s WEST.
E) 3.00 m/s WEST.

Question 59

A 8.00 kg mass is moving at 5.00 m/s SOUTH and a 6.00 kg mass is moving at 7.00 m/s EAST. Find the velocity of the center of mass, letting (a) = the east-west component, and (b) = the north-south component.

A) a = +0.50 m/s, b = +3.00 m/s.
B) a = +3.00 m/s, b = +2.86 m/s.
C) a = −3.00 m/s, b = −3.00 m/s.
D) a = +3.00 m/s, b = −2.86 m/s.
E) a = +42.0 m/s, b = −40.0 m/s.

Question 60

A 1200 kg car is moving at 5.0 m/s EAST. It strikes an 1800 kg car at rest. The cars undergo an elastic collision and move in the EAST or WEST direction. The velocity of the 1200 kg car after the collision is

A) 4.0 m /s EAST.
B) 1.0 m/s EAST.
C) 4.0 m/s WEST.
D) 1.0 m/s WEST.
E) 3.0 m/s EAST.

Question 61

A 4.00 kg object is moving at 5.00 m/s EAST. It strikes a 6.00 kg object that is at rest. The objects undergo an elastic collision. The velocity of the 4.00 kg object after the collision is at an angle of 30.0 degrees SOUTH of EAST. The speed of the 4.00 kg mass after the collision is

A) 5.78 m/s.
B) 4.56 m/s.
C) 3.55 m/s.
D) 1.67 m/s.
E) 2.66 m/s.

Question 62

A 4.00 kg object is moving at 5.00 m/s NORTH. It strikes a 6.00 kg object that is moving WEST at 2.00 m/s. The objects undergo a perfectly inelastic (stick together) collision. The kinetic energy lost in the collision is

A) 34.8 J.
B) 28.7 J.
C) 20.4 J.
D) 18.7 J.
E) 14.9 J.

Question 63

A 1200 kg car is moving at 5.0 m/s EAST. It strikes an 1800 kg car at rest. The cars undergo an elastic collision and move in the EAST or WEST direction. The velocity of the 1800 kg car after the collision is

A) 3.0 m/s WEST.
B) 1.0 m/s EAST.
C) 4.0 m/s EAST.
D) 4.0 m/s WEST.
E) 1.0 m/s WEST.

Question 64

A 4.00 kg object is moving at 5.00 m/s NORTHWEST. It strikes a 6.00 kg object that is moving SOUTHWEST at 2.00 m/s. The collision is perfectly inelastic. The kinetic energy lost in the collision is

A) 20.4 J.
B) 28.7 J.
C) 34.8 J.
D) 40.2 J.
E) 45.1 J.

Question 65

The Earth has a mass approximately 80 times that of the Moon. The distance between their centers is on average about 384000 km. How far from the center of the Earth is the center of mass of the Earth-Moon system?

A) Not enough information is given
B) 4800 km
C) 4860 km
D) 4740 km

Question 66

A 4.00 kg object is moving at 5.00 m/s NORTH. It strikes a 6.00 kg object that is moving EAST at 2.00 m/s. The objects undergo a perfectly inelastic (stick together) collision. The velocity of the 6.00 kg object after the collision is

A) 2.33 m/s at an angle of 35.0 degrees NORTH of EAST.
B) 2.33 m/s at an angle of 59.0 degrees NORTH of EAST.
C) 2.00 m/s at an angle of 59.0 degrees NORTH of EAST.
D) 2.00 m/s at an angle of 45.0 degrees NORTH of EAST.
E) 2.33 m/s at an angle of 45.0 degrees NORTH of EAST.

Question 67

A 1700 kg car travels at 20 m/s WEST and collides with a 2000 kg car traveling EAST. The collision is completely inelastic and they both come to rest. What was the velocity of the 2000 kg car?

A) 17 m/s EAST
B) 14 m/s EAST
C) 17 m/s WEST
D) 14 m/s WEST
E) 12 m/s EAST

Question 68

A 4.00 kg object is moving at 5.00 m/s EAST. It strikes a 6.00 kg object that is at rest. The objects collide elastically. The velocity of 4.00 kg object after the collision is in the SOUTHWEST direction. The speed of the 6.00 kg object after the collision is

A) 2.38 m/s.
B) 3.02 m/s.
C) 3.96 m/s.
D) 4.06 m/s.
E) 5.22 m/s.

Question 69

A binary star system is composed of two stars (one blue, one red) that orbit a common center of mass. Let the distances from the stars to the center of mass be labeled r_blue and r_red. The sum of the masses of the stars is M_blue + M_red = 3.70 x 10³³ kg. If it is known that r_blue = 2/5 r_red, what is M_red?

A) 1.06 × 10³³ kg
B) 2.64 × 10³³ kg
C) 1.48 × 10³³ kg
D) 2.22 × 10³³ kg

Question 70

A car accelerates from rest along a straight road, increasing its momentum from 0 to 52500 kg·m/s in 6.5 s. If its engine and tires are able to provide an average force of 8500 N, what is the magnitude of the net dissipative force (friction and air resistance) on the car during this interval?

A) 11450 N
B) 1840 N
C) 3510 N
D) 423 N

Question 71

A 4.00 kg object is moving at 5.00 m/s NORTHWEST. It strikes a 6.00 kg object that is moving SOUTHWEST at 2.00 m/s. The objects collide perfectly inelastically (stick together). The velocity of the 6.00 kg object after the collision is

A) 2.33 m/s at an angle of 45.0 degrees NORTH of WEST.
B) 3.89 m/s at an angle of 35.0 degrees NORTH of WEST.
C) 3.89 m/s at an angle of 14.0 degrees NORTH of WEST.
D) 2.33 m/s at an angle of 14.0 degrees NORTH of WEST.
E) 2.33 m/s at an angle of 35.0 degrees NORTH of WEST.

Question 72

A 1200 kg car is moving at 5.0 m/s EAST. It strikes an 1800 kg car at rest. The cars undergo an elastic collision and move in the EAST or WEST direction. The magnitude of the relative velocity between the cars after the collision is

A) 3.0 m/s.
B) 1.0 m/s.
C) 4.0 m/s.
D) 5.0 m/s.
E) 2.0 m/s.

Question 73

A 2200 kg truck slows down, reducing its momentum by 22000 kg·m/s in 3.2 s, as its driver sees a deer wander into the road. What is the magnitude of the average net force that slows the truck?

A) 8.3 kN
B) 23.4 kN
C) 6.9 kN
D) 15.1 kN

Question 74

In any collision

A) total momentum is not conserved.
B) total kinetic energy is conserved.
C) total momentum is conserved.
D) total momentum is not conserved but total kinetic energy is conserved.
E) total momentum and total kinetic energy are conserved.

Question 75

A ball collides with a second ball at rest. As a result of the collision, the first ball comes to rest and the second ball moves off at the speed of the first ball. In this collision

A) not enough information to say whether masses are equal or total kinetic energy is conserved.
B) the masses are unequal and total kinetic energy is not conserved.
C) the masses are unequal and total kinetic energy is conserved.
D) the masses are equal and total kinetic energy is not conserved.
E) the masses are equal and total kinetic energy is conserved.

Question 76

A vertical spring is compressed and, when released, applies a force during a 0.25 s time interval to a 17 g frog, which is flung upward due to the applied force from the spring. If the frog attains an upward velocity of 11 m/s after being released from the spring, what average upward force was applied by the spring?

A) 0.21 N
B) 0.91 N
C) 0.75 N
D) 0.17 N
E) 0.58 N

Question 77

A 4.00 kg object is moving at 5.00 m/s NORTH. It strikes a 6.00 kg object that is moving WEST at 2.00 m/s. The objects undergo a perfectly inelastic collision (stick together). The velocity of the 4.00 kg object after the collision is

A) 2.54 m/s at an angle of 35.0 degrees NORTH of WEST.
B) 1.93 m/s at an angle of 59.0 degrees NORTH of WEST.
C) 1.93 m/s at an angle of 45.0 degrees NORTH of WEST.
D) 2.33 m/s at an angle of 59.0 degrees NORTH of WEST.
E) 2.33 m/s at an angle of 45.0 degrees NORTH of WEST.

Question 78

A 1200 kg car travels at 25.0 m/s and collides head-on in a perfectly inelastic collision with a stationary 2400 kg truck. The kinetic energy lost in the collision is

A) 330,000 J.
B) 250,000 J.
C) 125,000 J.
D) 95,000 J.
E) 75,000 J.

Question 79

A 4.00 kg object is moving at 5.00 m/s SOUTH. It strikes a 3.00 kg object that is moving WEST at 2.00 m/s. The collision is perfectly inelastic. The kinetic energy lost in the collision is

A) 24.9 J.
B) 18.4 J.
C) 10.5 J.
D) 8.33 J.
E) 2.61 J.

Question 80

A pair of identical balls are connected by a massless rod and thrown straight up into the air, such that the center of mass of the pair reaches a maximum height of 13.2 m above the point of release. On the way up, when the center of mass is at 6.6 m above to point of release, the velocity of one ball is measured to be 7.7 m/s straight downward. What is the velocity of the other ball at this time? Ignore air resistance.

A) 30.2 m/s up
B) 23.8 m/s up
C) 19.1 m/s up
D) 15.7 m/s up
E) 3.7 m/s up