Deck 4: The Laws of Motion

Question 1

A barefoot field-goal kicker imparts a speed of 25 m/s to a football at rest.If the football has a mass of 0.50 kg and time of contact with the football is 0.020 s,what is the force exerted on the foot?

A) 13 N
B) 25 N
C) 625 N
D) 1,250 N
E) ​625 N

Answer 1

625 N

Question 2

A rock is rolled in the sand.It starts at 6.0 m/s,moves in a straight line for a distance of 4.5 m,and then stops.What is the magnitude of the average acceleration?

A) 1.7 m/s²
B) 4 m/s²
C) 1.5 m/s²
D) 0.3 m/s²
E) ​8 m/s²

Answer 2

4 m/s²

Question 3

A 1,500-kg sailboat experiences an eastward force of 3,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W).What is the magnitude of the resultant acceleration?

A) 2.9 m/s²
B) 5.9 m/s²
C) 4.6 m/s²
D) 6.3 m/s²
E) ​1.7 m/s²

Answer 3

2.9 m/s²

Question 4

The accelerating force of the wind on a small 150-kg sailboat is 756 N northeast.If the drag of the keel is 535 N acting west,what is the acceleration of the boat?

A) 8.6 m/s² due east
B) 3.6 m/s² due north
C) 5 m/s² northeast
D) 6.2 m/s² north by northwest
E) ​1.5 m/s² due east

Question 5

A 9.0-kg bowling ball experiences a net force of 6.0 N.What will be its acceleration?

A) 54 m/s²
B) 9.0 m/s²
C) 6.0 m/s²
D) 0.67 m/s²
E) ​1.5 m/s²

Question 6

A 2,000-kg sailboat experiences an eastward force of 2,500 N by the ocean tide and a wind force against its sails with magnitude of 6,000 N directed toward the northwest (45° N of W).What is the direction of the resultant acceleration?

A) 23° N of W
B) 12° N of W
C) 60° N of E
D) 68° N of W
E) ​68° N of E

Question 7

If we know an object is moving at constant velocity,we may assume:

A) the net force acting on the object is zero.
B) there are no forces acting on the object.
C) the object is accelerating.
D) the object is losing mass.

Question 8

What condition must apply to a system's state of motion for it to be regarded as an inertial frame of reference?

A) in decreasing velocity
B) in constant velocity
C) in constant acceleration
D) in increasing acceleration

Question 9

Two ropes are attached to a 35-kg object.The first rope applies a force of 20 N and the second,55 N.If the two ropes are perpendicular to each other,what is the resultant acceleration of the object?

A) 1.7 m/s²
B) 20 m/s²
C) 2.1 m/s²
D) 59 m/s²
E) 0.6 ​m/s²

Question 10

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.An astronaut's life support backpack weighs 350 lb on Earth.What does it weigh on the Moon?

A) 2,100 lb
B) 350 lb
C) 356 lb
D) 58 lb
E) ​344 lb

Question 11

Rita accelerates a 0.45-kg ball from rest to 8.0 m/s during the 0.15 s in which her foot is in contact with the ball.What average force does she apply to the ball during the kick?

A) 119 N
B) 27 N
C) 24 N
D) 54 N
E) ​3 N

Question 12

The acceleration due to gravity on the Moon's surface is one-sixth that on Earth.What net force would be required to accelerate a 15-kg object at 8.0 m/s² on the moon?

A) 1.9 N
B) 20 N
C) 720 N
D) 120 N
E) ​11.3 N

Question 13

If we know that a nonzero net force is acting on an object,which of the following must we assume regarding the object's condition? The object is:

A) at rest.
B) moving with a constant velocity.
C) being accelerated.
D) losing mass.

Question 14

An automobile of mass 3,000 kg moving at 45 m/s is braked suddenly with a constant braking force of 9,000 N.How far does the car travel before stopping?

A) 8 m
B) 338 m
C) 169 m
D) 507 m
E) ​18 m

Question 15

An astronaut applies a force of 450 N to an asteroid,and it accelerates at 9.00 m/s².What is the asteroid's mass?

A) 50 kg
B) 450 kg
C) 459 kg
D) 4,050 kg
E) ​0.02 kg

Question 16

Which of the following expresses a principle,which was initially stated by Galileo and was later incorporated into Newton's laws of motion?

A) An object's acceleration is inversely proportional to its mass.
B) For every action there is an equal but opposite reaction.
C) The natural condition for a moving object is to remain in motion.
D) The natural condition for a moving object is to come to rest.

Question 17

Two forces act on a 5.00-kg object.One of the forces is 11.0 N.If the object accelerates at 4.00 m/s²,what is the greatest possible magnitude of the other force?

A) 1.0 N
B) 9.0 N
C) 31.0 N
D) 16.7 N
E) ​51.0 N

Question 18

Which of the following is an example of the type of force that acts at a distance?

A) gravitational
B) magnetic
C) electrical
D) all of the above

Question 19

A cart of weight 25 N is accelerated across a level surface at 0.15 m/s².What net force acts on the wagon? (g = 9.8 m/s²)

A) 36.75 N
B) 0.38 N
C) 3.8 N
D) 17.01 N
E) ​166.7 N

Question 20

A 60.0-kg man jumps 1.00 m down onto a concrete walkway.His downward motion stops in 0.0400 seconds.If he forgets to bend his knees,what force is transmitted to his leg bones?

A) 6,600 N
B) 300 N
C) 2,900 N
D) 900 N
E) ​900 N

Question 21

A 15.0-kg block rests on a level frictionless surface and is attached by a light string to a 7.0-kg hanging mass where the string passes over a massless frictionless pulley.If g = 9.8 m/s²,what is the tension in the connecting string?

A) 3 N
B) 27 N
C) 129 N
D) 47 N
E) ​216 N

Question 22

A shot-putter moves his arm and the 6.0-kg shot through a distance of 2.5 m,giving the shot a velocity of 8 m/s from rest.Find the average force exerted on the shot during this time.

A) 154 N
B) 77 N
C) 58 N
D) 9 N
E) ​​480 N

Question 23

As a 4.0-kg bucket is being lowered into a 13-m-deep well,starting from the top,the tension in the rope is 9 N.The acceleration of the bucket will be:

A) 7.6 m/s² downward.
B) 9 m/s² downward.
C) zero.
D) 2.3 m/s² upward.
E) ​7.6 m/s² upward.

Question 24

Two blocks of masses 22 kg and 9 kg are connected together by a light string and rest on a frictionless level surface.Attached to the 9-kg mass is another light string,which a person uses to pull both blocks horizontally.If the two-block system accelerates at 0.7 m/s²,what is the tension in the second string attached to the 8-kg mass?

A) 21.7 N
B) 9.1 N
C) 15.4 N
D) 6.3 N
E) ​31 N

Question 25

As a basketball player starts to jump for a rebound,he begins to move upward faster and faster until he leaves the floor.During this time that he is in contact with the floor,the force of the floor on his shoes is:

A) bigger than his weight.
B) equal in magnitude and opposite in direction to his weight.
C) less than his weight.
D) zero.

Question 26

Three forces,10.0 N,20.0 N,and 15.0 N,are acting on a 9.23-kg object.Which of the following forces could also be acting on the object if it is moving with constant velocity?

A) 1.0 N
B) 19.0 N
C) 34.0 N
D) ​2.0 N
E) ​any of the above

Question 27

A thrown stone hits a window,but doesn't break it.Instead it reverses direction and ends up on the ground below the window.In this case,we know:

A) the force of the stone on the glass > the force of the glass on the stone.
B) the force of the stone on the glass = the force of the glass on the stone.
C) the force of the stone on the glass < the force of the glass on the stone.
D) the stone didn't slow down as it broke the glass.

Question 28

An airplane of mass 1.8 × 10⁴ kg tows a glider of mass 0.6 × 10⁴ kg.The airplane propellers provide a net forward thrust of 9.60 × 10⁴ N.What is the glider's acceleration?

A) 4.0 m/s²
B) 5.0 m/s²
C) 8.0 m/s²
D) 16.0 m/s²
E) ​9.8 m/s²

Question 29

An elevator weighing 19,000 N is supported by a steel cable.What is the tension in the cable when the elevator is being accelerated upward at a rate of 3.00 m/s²? (g = 9.80 m/s²)

A) 5,800 N
B) 19,000 N
C) 57,000 N
D) 24,800 N
E) ​6,300 N

Question 30

In the terminology a 500-N block,the 500-N refers to the block's:

A) mass.
B) force.
C) weight.
D) None of the above.

Question 31

A 5,500-N weight is held suspended in equilibrium by two cables.Cable 1 applies a horizontal force to the right of the object and has a tension,T₁.Cable 2 applies a force upward and to the left at an angle of 35.0° to the negative x-axis and has a tension,T₂.What is the tension,T₁?

A) 3,850 N
B) 7,860 N
C) 4,510 N
D) 9,590 N
E) ​11,710 N

Question 32

Two blocks of masses 24 kg and 9 kg are connected together by a light string and rest on a frictionless level surface.Attached to the 9-kg mass is another light string,which a person uses to pull both blocks horizontally.If the two-block system accelerates at 0.6 m/s² what is the tension in the connecting string between the blocks?

A) 19.8 N
B) 9 N
C) 14.4 N
D) 5.4 N
E) ​40 N

Question 33

Two blocks,joined by a string,have masses of 8.0 and 9.0 kg.They rest on a frictionless horizontal surface.A 2nd string,attached only to the 9.0-kg block,has horizontal force = 30 N applied to it.Both blocks accelerate.Find the tension in the string between the blocks.

A) 16 N
B) 2 N
C) 14 N
D) 64 N
E) ​240 N

Question 34

As I slide a box at constant speed up a frictionless slope,pulling parallel to the slope,the tension in the rope will be:

A) greater than the tension would be if the box were stationary.
B) greater than the weight of the box.
C) equal to the weight of the box.
D) less than the weight of the box.

Question 35

An object of mass m is on the surface of the Earth.The distance to the Sun and the Moon are d_S and d_M,and the masses of the Sun and Moon are M_S and M_M.What is the ratio of the gravitational force from the Sun to that of the Moon on the object?
​

A) M_SM_M /d_Sd_M
B) M_SM_M /d²_Sd²_M
C) M_Sd²_M /M_Md²_M
D) M_Md²_S /M_Sd²_M

Question 36

A 5,500-N weight is suspended in equilibrium by two cables.Cable 1 applies a horizontal force to the right of the object and has a tension,T₁.Cable 2 applies a force upward and to the left at an angle of 38.0° to the negative x-axis and has a tension,T₂.Find T_2.

A) 7,040 N
B) 3,390 N
C) 8,930 N
D) 6,980 N
E) ​4,330 N

Question 37

The statement by Newton that "for every action there is an opposite but equal reaction" is regarded as which of his laws of motion?

A) first
B) second
C) third
D) fourth

Question 38

A 9-kg mass and a 2-kg mass are connected by a light string over a massless,frictionless pulley.If g = 9.8 m/s²,what is the acceleration of the system when released?

A) 15.4 m/s²
B) 6.2 m/s²
C) 107.8 m/s²
D) 9.8 m/s²
E) ​1.1 m/s²

Question 39

A boxcar of mass 300 tons at rest becomes uncoupled on a 2.0° grade.If the track is considered to be frictionless,what speed does the boxcar have after 8 seconds?

A) 8.5 m/s
B) 0 m/s
C) 35.1 m/s
D) 2.7 m/s
E) ​0.3 m/s

Question 40

A baseball batter hits an incoming 45-m/s fastball.The ball leaves the bat at 50 m/s after a ball-on-bat contact time of 0.050 s.What is the force exerted on the 0.10-kg baseball?

A) 190 N
B) 10 N
C) 100 N
D) 48 N
E) ​90 N

Question 41

A 25-kg traffic light hangs midway on a cable between two poles 50 meters apart.If the sag in the cable is 0.40 meters,what is the tension in each side of the cable?

A) 120 N
B) 15,310 N
C) ​7,660 N
D) ​780 N
E) ​30,630 N

Question 42

A horizontal force of 750 N is needed to overcome the force of static friction between a level floor and a 350-kg crate.What is the acceleration of the crate if the 750-N force is maintained after the crate begins to move and the coefficient of kinetic friction is 0.13?

A) 0.9 m/s²
B) 3.4 m/s²
C) 2.7 m/s²
D) 1.3 m/s²
E) ​1.9 m/s²

Question 43

A 100-kg crate is placed on an adjustable inclined plane.If the crate slides down the incline with an acceleration of 0.20 m/s² when the incline angle is 20°,then what should the incline angle be for the crate to slide down the plane at constant speed? (g = 9.8 m/s²)

A) 24°
B) 19°
C) 14°
D) 29°
E) ​9°

Question 44

Doug hits a hockey puck,giving it an initial velocity of 5.0 m/s.If the coefficient of kinetic friction between ice and puck is 0.200,how far will the puck slide before stopping?

A) 11 m
B) 16 m
C) 6 m
D) 11 m.
E) ​21 m

Question 45

Three identical 4.0-kg cubes are placed on a horizontal frictionless surface in contact with one another.The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 4.0 m/s².What is the magnitude of the force exerted on the middle cube by the left cube in this case?

A) 16 N
B) 32 N
C) 48 N
D) ​64 N
E) ​none of the above

Question 46

A 150-kg crate is placed on an adjustable inclined plane.As one end of the incline is raised,the crate begins to move downward.If the crate slides down the plane with an acceleration of 0.40 m/s² when the incline angle is 25°,what is the coefficient of kinetic friction between ramp and crate? (g = 9.8 m/s²)

A) 0.52
B) 0.62
C) 0.42
D) 0.32
E) ​3.74

Question 47

Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another.The cubes are lined up from left to right and a force is applied to the left side of the left cube causing all three cubes to accelerate to the right at 4.0 m/s².What is the magnitude of the force exerted on the right cube by the middle cube in this case?

A) 24 N
B) 48 N
C) 72 N
D) ​96 N
E) ​none of the above

Question 48

A karate master strikes a board with an initial velocity of 18.0 m/s,decreasing to 4.0 m/s as his hand passes through the board.If the time of contact with the board is 0.002 s,and the mass of the coordinated hand and arm is 1.0 kg,what is the force exerted on the board?

A) 11,000 N
B) 0.028 N
C) 0.044 N
D) ​7,000 N
E) ​9,000 N

Question 49

Find the tension in an elevator cable if the 2,000-kg elevator is descending with an acceleration of 1.8 m/s²,downward.

A) 23,200 N
B) 16,000 N
C) 3,600 N
D) ​17.64 N
E) ​250.00 N

Question 50

It is late and Carlos is sliding down a rope from his third floor window to meet his friend Juan.As he slides down the rope faster and faster,he becomes frightened and grabs harder on the rope,increasing the tension in the rope.As soon as the upward tension in the rope becomes equal to his weight:

A) Carlos will stop.
B) Carlos will slow down.
C) Carlos will continue down at a constant velocity.
D) the rope must break.

Question 51

Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another.The cubes are lined up from left to right and a 36-N force is applied to the left side of the left cube causing all three cubes to accelerate to the right.If the cubes are each subject to a frictional force of 6.0 N,what is the magnitude of the force exerted on the middle cube by the left cube in this case?

A) 12 N
B) 24 N
C) 6.0 N
D) ​36 N
E) ​none of the above

Question 52

A 100-kg box is placed on a ramp.As one end of the ramp is raised,the box begins to move downward just as the angle of inclination reaches 10°.What is the coefficient of static friction between box and ramp?

A) 0.27
B) 0.18
C) 5.67
D) 0.13
E) ​17.36

Question 53

Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another.The cubes are lined up from left to right and a 36-N force is applied to the left side of the left cube causing all three cubes to accelerate to the right.If the cubes are each subject to a frictional force of 6.0 N,what is the magnitude of the force exerted on the right cube by the middle cube in this case?

A) 12 N
B) 24 N
C) 36 N
D) 6.0 N
E) ​none of the above

Question 54

A 600-N tightrope walker stands at the center of the rope such that each half of the rope makes an angle of 20.0° with the horizontal.What is the tension in the rope?

A) 880 N
B) 640 N
C) 1,750 N
D) 410 N
E) ​820 N

Question 55

A block of mass 2.00 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.200.A string attached to the block is pulled horizontally,resulting in a 2-m/s² acceleration by the block.Find the tension in the string.(g = 9.80 m/s²)

A) 4 N
B) 3.92 N
C) 7.92 N
D) 0.08 N
E) 2.00​ N

Question 56

A sled weighs 200 N.It is held in place on a frictionless 20° slope by a rope attached to a stake at the top;the rope is parallel to the slope.What is the normal force of the slope acting on the sled?

A) 188 N
B) 68 N
C) 213 N
D) 585 N
E) ​73 N

Question 57

A sled weighs 200 N.It is held in place on a frictionless 15° slope by a rope attached to a stake at the top;the rope is parallel to the slope.Find the tension in the rope.

A) 193 N
B) 773 N
C) 207 N
D) 52 N
E) ​54 N

Question 58

A 500-N tightrope walker stands at the center of the rope.If the rope can withstand a tension of 2,000 N without breaking,what is the minimum angle the rope can make with the horizontal?

A) 83°
B) 7°
C) 14°
D) 1°
E) ​8°

Question 59

A girl is using a rope to pull a box that weighs 350 N across a level surface with constant velocity.The rope makes an angle of 30° above the horizontal,and the tension in the rope is 100 N.What is the normal force of the floor on the box?

A) 400 N
B) 250 N
C) 450 N
D) 300 N
E) ​263 N

Question 60

A horizontal force of 950 N is needed to overcome the force of static friction between a level floor and a 150-kg crate.If g = 9.8 m/s²,what is the coefficient of static friction?

A) 64.63
B) ​6.46
C) 1.55
D) 0.65
E) ​6.33

Question 61

The coefficient of friction between a racecar's wheels and the track is 1.0.The car starts from rest and accelerates at a constant rate for 700 m.Find the maximum speed at the end of the race.

A) 83 m/s
B) 91 m/s
C) 117 m/s
D) 125 m/s
E) ​105 m/s

Question 62

A 18-kg mass is placed on a 28° incline and friction keeps it from sliding.The coefficient of static friction in this case is 0.591,and the coefficient of sliding friction is 0.511.What is the frictional force in this situation?

A) 82.81 N
B) 155.75 N
C) 79.59 N
D) 92.05 N
E) ​8.45 N

Question 63

A 300-N sled is pulled up a 27° slope at a constant speed by a force of 250 N.What is the coefficient of kinetic friction between sled and slope?

A) 0.25
B) 0.85
C) 0.13
D) 1.67
E) ​2.89

Question 64

Hector drives a pickup truck horizontally at 10.0 m/s.He is transporting a crate of delicate lead crystal.If the coefficient of static friction between the crate and the truck bed is 0.700,what is the minimum stopping distance for the truck so the crate will not slide?

A) 7.3 m
B) 14.0 m
C) 100.0 m
D) 17.3 m
E) ​3.6 m

Question 65

Dana uses a rope to pull a box that weighs 300 N across a level surface with constant velocity.The rope makes an angle of 25° above the horizontal and the tension in the rope is 100 N.What is the coefficient of friction?

A) 0.35
B) 0.20
C) 0.50
D) 2.14
E) ​0.47

Question 66

A 12-kg mass is placed on a 29° incline and friction keeps it from sliding.The coefficient of static friction in this case is 0.633,and the coefficient of sliding friction is 0.524.The mass is given a shove causing it to slide down the incline.What is the frictional force while the mass is sliding?

A) 57.01 N
B) 102.86 N
C) 53.90 N
D) 65.11 N
E) ​10.50 N

Question 67

Jamal pulls a 250-N sled up a 25.0° slope at constant speed by a force of 200 N.Near the top of the hill he releases the sled.With what acceleration does the sled go down the hill?

A) 7.84 m/s²
B) 9.92 m/s²
C) 0.88 m/s²
D) 0.44 m/s²
E) ​1.44 m/s²

Question 68

Two objects,A and B,are placed on an inclined plane that can be rotated to different angles of elevation.A starts to slide at twice the angle of elevation that B starts sliding.The respective coefficients for static friction for A and B are μ_A and μ_B.Choose the last answer that is correct.

A) μ_B > μ_A
B) μ_A > μ_B
C) μ_B = 2 μ_A
D) μ_A = 2 μ_B

Question 69

A trapeze artist,with swing,weighs 800 N;he is being held to one side by his partner so that the swing ropes make an angle of 45.0° with the vertical.In such a condition of static equilibrium,what is the tension in the rope?

A) 1,131 N
B) 566 N
C) 800 N
D) 1,600 N
E) ​1,181 N

Question 70

A hockey puck moving at 9.0 m/s coasts to a halt in 85 m on a smooth ice surface.What is the coefficient of friction between the ice and the puck?

A) μ = 0.219
B) μ = 0.049
C) μ = 0.097
D) μ = 0.146
E) ​μ = 0.243

Question 71

A trapeze artist,with swing,weighs 600 N;he is momentarily held to one side by his partner so that the swing ropes make an angle of 45° with the vertical.In such a condition of static equilibrium,what is the horizontal force being applied by the partner?

A) 424 N
B) 386 N
C) 300N
D) 600 N
E) ​200 N

Question 72

A man pulls a sled at a constant velocity across a horizontal snow surface.If a force of 85 N is being applied to the sled rope at an angle of 50° to the ground,what is the force of friction between sled and snow?

A) 85 N
B) 65 N
C) 55 N
D) 6 N
E) ​43 N

Question 73

A worker pulls a 350-N packing crate at constant velocity across a rough floor by exerting a force F = 200.0 N at an angle of 30.0° above the horizontal.What is the coefficient of kinetic friction of the floor?

A) 0.793
B) 0.693
C) ​0.593
D) ​1.386
E) ​0.400

Question 74

As a car moves forward on a level road at constant velocity,the net force acting on the tires is:

A) greater than the normal force times the coefficient of static friction.
B) equal to the normal force times the coefficient of static friction.
C) the normal force times the coefficient of kinetic friction.
D) zero.

Question 75

As a car skids with its wheels locked trying to stop on a road covered with ice and snow,the force of friction between the icy road and the tires will usually be:

A) greater than the normal force of the road times the coefficient of static friction.
B) equal to the normal force of the road times the coefficient of static friction.
C) less than the normal force of the road times the coefficient of static friction.
D) greater than the normal force of the road times the coefficient of kinetic friction.

Question 76

There are five books in a stack,each with a weight of 8N.The coefficient of friction between all the books is 0.4 as is the coefficient between the table and the bottom book.What horizontal push must I just exceed on the next to bottom book to start sliding the top four books off the bottom one?

A) 3.2 N
B) 12.8 N
C) 1.6 N
D) 16 N
E) ​32 N

Question 77

A 479-N crate rests on an ramp;the maximum angle just before it slips is 20° with the horizontal.What is the coefficient of static friction between crate and ramp surfaces?

A) 2.75
B) 0.58
C) 1.73
D) 0.36
E) ​0.72

Question 78

A 17-kg mass is placed on a 28° incline and friction keeps it from sliding.The coefficient of static friction in this case is 0.565 and the coefficient of sliding friction is 0.515.The mass is given a shove causing it to slide down the incline.Taking down the incline as positive,what is the acceleration of the mass while it is sliding?

A) -0.14 m/s²
B) 0.14 m/s²
C) -0.29 m/s²
D) 0.29 m/s²
E) ​15.01 m/s²

Question 79

As a car goes up a hill,there is a force of friction between the road and the tires rolling on the road.The maximum force of friction is equal to:

A) the weight of the car times the coefficient of kinetic friction.
B) the normal force of the road times the coefficient of kinetic friction.
C) the normal force of the road times the coefficient of static friction.
D) zero.

Question 80

An Olympic skier moving at 15.0 m/s down a 25.0° slope encounters a region of wet snow,of coefficient of friction μ_k = 0.740.How far down the slope does she go before stopping?

A) 56 m
B) 46 m
C) 66 m
D) 36 m
E) ​61 m