Deck 6: Momentum, Impulse, and Collisions

Question 1

A 70-kg swimmer dives horizontally off a 500-kg raft.The diver's speed immediately after leaving the raft is 6.0 m/s.A micro-sensor system attached to the edge of the raft measures the time interval during which the diver applies an impulse to the raft just prior to leaving the raft surface.If the time interval is read as 0.25 s,what is the magnitude of the average horizontal force by diver on the raft?

A)110 N
B)420 N
C)2 000 N
D)1 700 N
E)24 N

Answer 1

1 700 N

Question 2

The impulse experienced by a body is equivalent to its change in:

A)velocity.
B)kinetic energy.
C)momentum.
D)None of the above choices are valid.

Answer 2

momentum.

Question 3

The dimensional equivalent of the quantity impulse in terms of the fundamental quantities (mass,length,time)is which of the following?

A)MLT−¹
B)ML²T−²
C)MLT
D)MLT−²

Answer 3

MLT−¹

Question 4

In an automobile collision,how does an airbag lessen the blow to the passenger? Assume as a result of the collision,the passenger stops.

A)The air bag decreases the momentum change of the passenger in the collision.
B)During the collision,the force from the air bag is greater than would be the force from the windshield or dashboard so the passenger cannot hit the hard objects.
C)The stopping impulse is the same for either the hard objects or the airbag.Unlike the windshield or dashboard,the air bag increases the time for the slowing process and thus decreases the average force on the passenger.
D)The airbag is there to insure the seatbelt holds.

Question 5

The dimensional equivalence of the quantity "momentum" in terms of the fundamental quantities (mass,length,time)is:

A)MLT−¹.
B)ML²T−².
C)MLT.
D)MLT−².

Question 6

Alex throws a 0.25-kg rubber ball down onto the floor.The ball's speed just before impact is 4.5 m/s,and just after is 2.9 m/s.What is the change in the magnitude of the ball's momentum?

A)0.39 kg⋅m/s
B)1.9 kg⋅m/s
C)1.1 kg⋅m/s
D)0.73 kg⋅m/s
E)7.4 kg⋅m/s

Question 7

A 0.10-kg ball is moving at 7.0 m/s when it is hit by a bat,causing it to reverse direction and have a speed of 12.0 m/s.What is the change in the magnitude of the momentum of the ball?

A)0.50 kg⋅m/s
B)5.0 kg⋅m/s
C)0.70 kg⋅m/s
D)1.9 kg⋅m/s
E)1.2 kg⋅m/s

Question 8

A car wash nozzle directs a steady stream of water at 1.10 kg/s,with a speed of 30.0 m/s,against a car window.What force does the water exert on the glass? Assume the water does not splash back.

A)27.3 N
B)33.0 N
C)31.1 N
D)0.367 N
E)1.10 N

Question 9

The units of impulse are equivalent to:

A)those of energy.
B)N⋅m.
C)kg⋅m/s.
D)those of force.

Question 10

A valid unit for momentum is which of the following?

A)kg⋅m/s²
B)kg/m²
C)kg⋅m/s
D)N⋅m

Question 11

A ball with original momentum +7.0 kg⋅m/s hits a wall and bounces straight back without losing any kinetic energy.The change in momentum of the ball is:

A)0.
B)14 kg⋅m/s.
C)7.0 kg⋅m/s.
D)-14 kg⋅m/s.
E)-7.0 kg⋅m/s.

Question 12

Two masses m₁ and m₂,with m₁ < m₂,have momenta with equal magnitudes.How do their kinetic energies compare?

A)KE₁ < KE₂
B)KE₁ = KE₂
C)KE₁ > KE₂
D)More information is needed.

Question 13

A soccer ball (mass = 0.43 kg)is moving at a speed of 20 m/s when it is kicked with a force of 300 N resulting in it going in the opposite direction with the same speed as before.What is the magnitude of the impulse delivered to the ball?

A)0,because the before and after momenta cancel each other.
B)8.6 kg·m/s
C)17 kg·m/s
D)2 600 kg·m/s

Question 14

A rock is moving with speed v.If the mass of the rock were tripled and the speed were reduced to v/3,which of the following statements would be true?

A)The kinetic energy of the rock is smaller than in the first case,but the momentum is larger.
B)The kinetic energy of the rock is smaller than in the first case,but the momenta of both are the same.
C)The kinetic energies of the rocks are the same in both cases.
D)The kinetic energy of the rock is 1/9 its previous value.

Question 15

Lonnie pitches a baseball of mass 0.500 kg.The ball arrives at home plate with a speed of 35.0 m/s and is batted straight back to Lonnie with a return speed of 50.0 m/s.If the bat is in contact with the ball for 0.055 s,what is the impulse experienced by the ball?

A)7.50 N⋅s
B)42.5 N⋅s
C)773 N⋅s
D)17.5 N⋅s
E)25.0 N⋅s

Question 16

The law of conservation of momentum is applicable to systems made up of objects described by which of the following?

A)macroscopic
B)microscopic
C)interacting through friction
D)All the above choices are valid.

Question 17

Jerome pitches a baseball of mass 0.300 kg.The ball arrives at home plate with a speed of 40.0 m/s and is batted straight back to Jerome with a return speed of 52.0 m/s.What is the magnitude of change in the ball's momentum?

A)3.60 kg⋅m/s
B)12.0 kg⋅m/s.
C)15.6 kg⋅m/s
D)27.6 kg⋅m/s
E)12.0 kg⋅m/s

Question 18

A crane drops a 0.250-kg steel ball onto a steel plate.The ball's speeds just before impact and after are 4.00 m/s and 3.70 m/s,respectively.If the ball is in contact with the plate for 0.035 s,what is the magnitude of the average force that the ball exerts on the plate during impact?

A)55.0 N
B)2.14 N
C)28.6 N
D)26.4 N
E)1.93 N

Question 19

Alex throws a 0.250-kg rubber ball down onto the floor.The ball's speed just before impact is 5.30 m/s,and just after is 3.71 m/s.If the ball is in contact with the floor for 0.028 s,what is the magnitude of the average force applied by the floor on the ball?

A)80.4 N
B)14.2 N
C)47.3 N
D)33.1 N
E)2.25 N

Question 20

If a glass of water is on a table with a piece of paper under it,it is relatively easy to pull the paper out without disturbing the glass very much if the pull is done very quickly.This is because,with a quick pull:

A)the force on the glass will be less.
B)the momentum of the paper will be greater.
C)the time for the pull will be less.
D)the coefficient of kinetic friction will be less.

Question 21

A 5.25-g bullet is fired into a 360-g block of wood suspended as a ballistic pendulum.The combined mass swings up to a height of 8.75 cm.What was the magnitude of the momentum of the combined mass immediately after the collision?

A)0.338 kg·m/s
B)0.471 kg·m/s
C)0.478 kg·m/s
D)0.626 kg·m/s
E)0.239 kg·m/s

Question 22

A 75.0-kg swimmer dives horizontally off a 465-kg raft initially at rest.If the diver's speed immediately after leaving the raft is 5.00 m/s,what is the corresponding raft speed?

A)31.0 m/s
B)375 m/s
C)0.806 m/s
D)1.24 m/s
E)5.00 m/s

Question 23

A high-diver of mass 59.8 kg jumps off a board 10.0 m above the water.If,1.00 s after entering the water his downward motion is stopped,what average upward force did the water exert?

A)108 N
B)4.27 N
C)840 N
D)598 N
E)None of the other answers is correct.

Question 24

If the momentum of an object is tripled,its kinetic energy will change by what factor?

A)zero
B)one-third
C)three
D)nine

Question 25

A cannon of mass 1 300 kg fires a 13.6-kg shell with a velocity of 180 m/s at an angle of 45° above the horizontal.Find the recoil velocity of the cannon across the level ground.

A)1.88 m/s
B)1.33 m/s
C)0.376 m/s
D)0.666 m/s
E)0.942 m/s

Question 26

The kinetic energy of an object is quadrupled.Its momentum will change by what factor?

A)zero
B)two
C)eight
D)four

Question 27

A billiard ball collides in an elastic head-on collision with a second identical ball.What is the kinetic energy of the system after the collision compared to that before collision?

A)the same as
B)one fourth
C)twice
D)four times

Question 28

Ann the Astronaut weighs 65.0 kg.She is space walking outside the space shuttle and pushes a 350.0-kg satellite away from the shuttle at 0.70 m/s.What speed does this give Ann as she moves toward the shuttle?

A)0.13 m/s
B)3.8 m/s
C)590 m/s
D)290 m/s
E)7.7 m/s

Question 29

Object 1 has twice the mass of Object 2.Both objects have the same kinetic energy.Which of the following statements is true?

A)Both objects can have the same magnitude of momentum.
B)Object 1 has a momentum of greater magnitude than Object 2.
C)The magnitude of the momentum of Object 2 is four times that of Object 1.
D)All the statements are false.

Question 30

A lump of clay is thrown at a wall.A rubber ball of identical mass is thrown with the same speed toward the same wall.Which statement is true?

A)The clay experiences a greater change in momentum than the ball.
B)The ball experiences a greater change in momentum than the clay.
C)The clay and the ball experience the same change in momentum.
D)It is not possible to know which object has the greater change in momentum.

Question 31

Three satellites are launched into space connected together.Once in deep space,an explosive charge separates the three satellites and they move apart.The satellites each have different masses with m₁ < m₂ < m₃.Which of the following statements is always true?

A)The one with mass m₁ receives the greatest impulse.
B)The one with mass m₃ receives the greatest impulse.
C)The all must receive equal impulses.
D)Although one or more of the above statements could be true in special cases,they are not always true.

Question 32

A uranium nucleus (mass 238 units)at rest decays into a helium nucleus (mass 4.0 units)and a thorium nucleus (mass 234 units).If the speed of the helium nucleus is 5.5 × 10⁵ m/s,what is the speed of the thorium nucleus?

A)9.4E+3 m/s
B)3.2E+7 m/s
C)3.4E+3 m/s
D)9.4E+7 m/s
E)1.9E-1 m/s

Question 33

A billiard ball collides in an elastic head-on collision with a second stationary identical ball.After the collision which of the following conditions applies to the first ball?

A)maintains the same velocity as before
B)has one half its initial velocity
C)comes to rest
D)moves in the opposite direction

Question 34

A 75-kg man is standing in a 20-kg boat.The man steps to the right thinking he is stepping out onto the dock.However,the following will actually happen (ignore the friction of the water or air on the boat or the man):

A)The man only moves a short distance to the right while the boat moves a larger distance to the left.
B)The man only moves a short distance to the left while the boat moves a larger distance to the right.
C)The man actually stays still while the boat moves toward the left.
D)The boat doesn't move and the man moves to the right.
E)​None of the above.

Question 35

A man standing on frictionless ice throws a 1.00-kg mass at 29.0 m/s at an angle of elevation of 50.0°.What was the magnitude of the man's momentum immediately after throwing the mass?

A)45.1 kg·m/s
B)18.6 kg·m/s
C)22.2 kg·m/s
D)37.9 kg·m/s
E)This cannot be answered because the mass of the man needs to be known.

Question 36

A 13.4-g bullet is fired into a 1.60-kg block of wood which is suspended as a ballistic pendulum.The combined mass swings up to a height of 8.50 cm.What was the kinetic energy of the combined mass immediately after the collision?

A)1.32 J
B)1.33 J
C)0.0112 J
D)1.34 J
E)0.137 J

Question 37

A machine gun is attached to a railroad flatcar that rolls with negligible friction.If the railroad car has a mass of 6.35 × 10⁴ kg,how many bullets of mass 35.0 g would have to be fired at 200 m/s off the back to give the railroad car a forward velocity of 0.56 m/s?

A)5.1E-4
B)2.0E+3
C)6.5E+5
D)5.1E+3
E)6.5E+4

Question 38

A 5.00-g bullet is fired into a 950-g block of wood suspended as a ballistic pendulum.The combined mass swings up to a height of 8.00 cm.What was the kinetic energy of the bullet immediately before the collision?

A)1.4E+2 J
B)1.5E+3 kJ
C)3.9E-3 J
D)1.4E+8 J
E)1.5E+2 J

Question 39

A moderate force will break an egg.However,an egg dropped on the road usually breaks,while one dropped on the grass usually doesn't break.This is because for the egg dropped on the grass:

A)the change in momentum is greater.
B)the change in momentum is less.
C)the time interval for stopping is greater.
D)the time interval for stopping is less.

Question 40

Object 1 has twice the mass of Object 2.Each of the objects has the same magnitude of momentum.Which of the following statements is true?

A)Both objects can have the same kinetic energy.
B)One object has 0.707 times the kinetic energy of the other.
C)One object has twice the kinetic energy of the other.
D)One object has 4 times the kinetic energy of the other.

Question 41

In a system with two moving objects,when a collision occurs between the objects:

A)the total kinetic energy is always conserved.
B)the total momentum is always conserved.
C)the total kinetic energy and total momentum are always conserved.
D)neither the kinetic energy nor the momentum is conserved.

Question 42

In a partially elastic collision between two objects with unequal mass:

A)the velocity of one will increase by the amount that the velocity of the other decreases.
B)the momentum of one will increase by the amount that the momentum of the other decreases.
C)the energy of one increases by the amount that the energy of the other decreases.
D)the total momentum of the system will decrease.

Question 43

A 26.0-g bullet moving at 1 200 m/s is fired through a one-kg block of wood emerging at a speed of 200 m/s.What is the kinetic energy of the block that results from the collision if the block had not been moving prior to the collision and was free to move?

A)6.6E+2 J
B)4.9E+2 J
C)3.4E+2 J
D)7.4E+2 J
E)1.3E+3 J

Question 44

Two skaters,both of mass 75.0 kg,are on skates on a frictionless ice pond.One skater throws a 0.40-kg ball at 6.0 m/s to his friend,who catches it and throws it back at 6.0 m/s.When the first skater has caught the returned ball,what is the velocity of each of the two skaters?

A)0.031 m/s,moving apart
B)0.063 m/s,moving apart
C)0.031 m/s,moving towards each other
D)0.063 m/s,moving towards each other
E)12 m/s,moving apart

Question 45

Kaitlin uses a bat to hit a thrown baseball.She knocks the ball back in the direction from which it came in a partially inelastic collision.The bat,which is heavier than the baseball,continues to move in the same direction after the hit as Kaitlin "follows through." Is the ball moving faster before or after it was hit?

A)The ball was moving faster before it was hit.
B)The ball was moving faster after it was hit.
C)The ball was moving at essentially the same speed before and after the hit.
D)There is insufficient information to answer this problem.

Question 46

A 2 900-kg truck moving at 11.0 m/s strikes a car waiting at a traffic light,hooking bumpers.The two continue to move together at 7.00 m/s.What was the mass of the struck car?

A)4 750 kg
B)7 460 kg
C)1 760 kg
D)1 660 kg
E)4 560 kg

Question 47

An object of mass m moving at speed v₀ strikes an object of mass 2m which had been at rest.The first object bounces backward along its initial path at speed v₀.Is this collision elastic,and if not,what is the change in kinetic energy of the system?

A)The collision is elastic.
B)The kinetic energy decreases by mv².
C)The kinetic energy decreases by mv²/2.
D)The kinetic energy increases by mv².

Question 48

A tennis ball is held above and in contact with a basketball,and then both are simultaneously dropped.The tennis ball bounces off the basketball at a fairly high speed.This is because:

A)the basketball falls farther than the tennis ball.
B)the tennis ball is slightly shielded from the Earth's gravitational pull.
C)the massive basketball transfers momentum to the lighter tennis ball.
D)the tennis ball has a smaller radius.

Question 49

In a two-body collision,if the kinetic energy of the system is conserved,then which of the following best describes the momentum after the collision?

A)must be less
B)must also be conserved
C)may also be conserved
D)is doubled in value

Question 50

When a collision is perfectly inelastic,then:

A)all the kinetic energy is conserved.
B)all the kinetic energy is gone.
C)the participants stick together.
D)the total momentum is zero.

Question 51

A 5-kg object is moving to the right at 4 m/s and collides with another object moving to the left at 5 m/s.The objects collide and stick together.After the collision,the combined object:

A)is moving to the right.
B)is moving to the left.
C)is at rest.
D)has less kinetic energy than the system had before the collision.

Question 52

Two billiard balls have velocities of 4.0 m/s and -1.0 m/s when they meet in an elastic head-on collision.What is the final velocity of the first ball after collision?

A)+1.0 m/s
B)-1.0 m/s
C)-3.0 m/s
D)+5.0 m/s
E)​+4.0 m/s

Question 53

Popeye,of mass 75.0 kg,has just downed a can of spinach.He accelerates quickly and stops Bluto,of mass 650 kg (Bluto is very dense),who is charging in at 15.0 m/s.What was Popeye's speed?

A)1.73 m/s
B)48.3 m/s
C)120 m/s
D)130 m/s
E)15.0 m/s

Question 54

Two particles collide,one of them initially being at rest.Is it possible for both particles to be at rest after the collision?

A)If the collision is perfectly inelastic,then this happens.
B)If the collision is elastic,then this happens.
C)This can happen sometimes if the more massive particle was at rest.
D)No.

Question 55

A 7.50-kg bowling ball strikes a 5.20-kg pin.The pin flies forward with a velocity of 4.00 m/s;the ball continues forward at 5.50 m/s.What was the original velocity of the ball?

A)11.3 m/s
B)8.27 m/s
C)0.128 m/s
D)1.34 m/s
E)4.61 m/s

Question 56

A 20.0-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s.If the block had been originally at rest and is free to move,what is its resulting speed?

A)22.0 m/s
B)18.0 m/s
C)20.0 m/s
D)2.00 m/s
E)45.0 m/s

Question 57

Two objects,one less massive than the other,collide elastically and bounce back after the collision.If the two originally had velocities that were equal in size but opposite in direction,then which one will be moving faster after the collision?

A)The less massive one.
B)The more massive one.
C)The speeds will be the same after the collision.
D)There is no way to be sure without the actual masses.

Question 58

During a snowball fight two balls with masses of 0.30 and 0.70 kg,respectively,are thrown in such a manner that they meet head-on and combine to form a single mass.The magnitude of initial velocity for each is 12.0 m/s.What is the speed of the 1.0-kg mass immediately after collision?

A)zero
B)4.8 m/s
C)12 m/s
D)8.4 m/s
E)3.6 m/s

Question 59

Two identical 7-kg bowling balls roll toward each other.The one on the left is moving at +4 m/s while the one on the right is moving at −4 m/s.What is the velocity of each ball after they collide elastically?

A)Neither is moving.
B)−4 m/s,+4 m/s
C)+4 m/s,−4 m/s
D)−14 m/s,+14 m/s
E)​+14 m/s,-14 m/s

Question 60

In a two-body collision,if the momentum of the system is conserved,then which of the following best describes the kinetic energy after the collision?

A)must be less
B)must also be conserved
C)may also be conserved
D)is doubled in value

Question 61

​A satellite engine has an exhaust speed of 2.80 × 10⁴ m/s and ejects ionized gas at a rate of 2.50 × 10^-6 kg/s.What is the instantaneous thrust of the engine?

A)8.93 × 10^-11 N
B)​7.00 × 10^-2 N
C)​​5.30 × 10² N
D)​1.12 × 10¹⁰ N

Question 62

Two masses m₁ and m₂,with m₁ = 3 m₂,undergo a head-on elastic collision.If the particles were approaching with speed v before the collision,with what speed are they moving apart after collision?

A)3 v
B)v/3
C)3v/4
D)v

Question 63

In an inelastic collision between two objects with unequal masses:

A)the velocity of one will increase by the amount that the velocity of the other decreases.
B)the momentum of one will increase by the amount that the momentum of the other decreases.
C)the energy of one increases by the amount that the energy of the other decreases.
D)the total momentum of the system will decrease.

Question 64

Two masses collide and stick together.Before the collision one of the masses was at rest.Is there a situation in which the kinetic energy is conserved in such a collision?

A)Yes,if the less massive particle is the one initially at rest.
B)Yes,if the more massive particle is the one initially at rest.
C)Yes,if the two particles have the same mass.
D)No,kinetic energy is always lost is such a collision.

Question 65

A billiard ball is moving in the x-direction at 33.4 cm/s and strikes another billiard ball moving in the y-direction at 38.9 cm/s.As a result of the collision,the first ball moves at 50.6 cm/s,and the second ball stops.In what final direction does the first ball move?

A)in the x-direction
B)at an angle of 49.4° ccw from the x-direction
C)at an angle of 40.6° ccw from the x-direction
D)at an angle of 56.6° ccw from the x-direction
E)Such a collision cannot happen.

Question 66

Three masses are moving along the x-axis.Their masses and velocities are ​m​₁ = ​m​ with ​v_​1 = ​v​,​m_​2 = 2​m with v₂ = 2v,and m₃ = 3m with v₃ = -3v ​(the minus sign indicating this velocity is in the negative x-direction).The three masses collide and stick together in a completely inelastic collision.What is the resultant velocity of the combined mass?

A)0,since their combined momentum is zero.
B)-2v/3
C)14v/3
D)-v

Question 67

Mitch throws a 130-g lump of clay at a 590-g target,which is at rest on a horizontal surface.After impact,the target,including the attached clay,slides 2.8 m before stopping.If the coefficient of friction is μ = 0.50,find the speed of the clay before impact.

A)6.4 m/s
B)33 m/s
C)29 m/s
D)0.62 m/s
E)34 m/s

Question 68

A 75.0-kg halfback running north with a speed of 11.0 m/s is tackled by a 80.5-kg opponent running south at 7.5 m/s.The collision is perfectly inelastic.Compute the velocity of the two players just after the tackle.

A)9.2 m/s south
B)1.4 m/s south
C)1.4 m/s north
D)40 m/s north
E)9.2 m/s north

Question 69

A disk of mass m moving in the positive x direction collides with a stationary disk,also of mass m.The first disk moves in a direction θ₁ with respect to the x axis,and the second disk moves off in a direction of θ₂ below the x axis,as shown in the figure.
If v = 10 m/s,θ₁ = 30°,and v_1f = 8 m/s,what is v_2f?

A)6.9 m/s
B)6.1 m/s
C)2.0 m/s
D)8.7 m/s

Question 70

A 25.0-kg object sitting at rest is struck elastically in a head-on collision with a 20.5-kg object initially moving at +4.0 m/s.Find the final velocity of the 25.0-kg object after the collision.

A)−0.90 m/s
B)−3.6 m/s
C)+6.6 m/s
D)+3.6 m/s
E)+15 m/s

Question 71

A baseball infielder,mass 78.0 kg,jumps up with velocity 3.50 m/s and catches a 0.195-kg baseball moving horizontally at 55.0 m/s.Of the following,which is closest to the final momentum of the system,infielder and baseball?

A)273 kg⋅m/s
B)328 kg⋅m/s
C)284 kg⋅m/s
D)240 kg⋅m/s
E)293 kg⋅m/s

Question 72

If a two-body collision is not head-on,then we may always assume that:

A)momentum is conserved.
B)kinetic energy is conserved.
C)neither momentum nor kinetic energy are conserved.
D)both momentum and kinetic energy are conserved.

Question 73

A neutron in a nuclear reactor makes an elastic head-on collision with a carbon atom initially at rest.(The mass of the carbon atom is 12 times that of the neutron. )What fraction of the neutron's kinetic energy is transferred to the carbon atom?

A)14.4%
B)28.4%
C)41.4%
D)56.6%

Question 74

A 1 000-kg vehicle is moving in the positive y-direction along the y-axis at 10 m/s.A 2 000-kg vehicle is moving in the positive x-direction at along the x-axis at 20 m/s.The vehicles collide and stick together.They move as a single object in a direction θ as measured counterclockwise from the x-axis immediately after the collision.What is the value of tan θ?

A)2.0
B)4.0
C)0.50
D)0.25

Question 75

A 2 500-kg car moving north collides with a 2 000-kg car moving west.After the collision,the cars stick together and move at an angle of 45° north of west at a speed of 8.0 m/s.What was the initial speed of the 2 500-kg car?

A)20 m/s
B)10.2 m/s
C)14 m/s
D)9.3 m/s

Question 76

A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s.As a result of the collision,the first ball moves at 50.0 cm/s,and the second ball stops.What is the change in kinetic energy of the system as a result of the collision?

A)0
B)some positive value
C)some negative value
D)No answer above is correct.

Question 77

A railroad freight car,mass 15 000 kg,is allowed to coast along a level track at a speed of 3.0 m/s.It collides and couples with a 54 000-kg loaded second car,initially at rest and with brakes released.What percentage of the initial kinetic energy of the 15 000-kg car is preserved in the two-coupled cars after collision?

A)78%
B)22%
C)18%
D)38%
E)14%

Question 78

A rocket has an exhaust speed of 2.5 × 10³ m/s,and produces 7.5 × 10⁵ N of instantaneous thrust.What mass of fuel does the rocket burn each second?

A)3.30 × 10^-3 kg/s
B)17.1 kg/s
C)300 kg/s
D)1.90 × 10⁹ kg/s

Question 79

A 5-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 5 m/s.The objects collide and stick together.After the collision,the combined object:

A)has the same kinetic energy that the system had before the collision.
B)has more kinetic energy than the system had before the collision.
C)has no kinetic energy.
D)has less momentum than the system had before the collision.

Question 80

A 22.3-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s.What is the change in the kinetic energy of the bullet-block system as a result of the collision assuming the block is free to move?

A)0 J
B)10.8 kJ
C)-10.8 kJ
D)11.2 J
E)223 J