Deck 4: Newtons Laws

Question 1

The figure below shows two forces,F_{1< / sub> and F2< / sub>,acting on an object. Use the vector diagrams to answer the question.
A third force is applied on the object so that the net force on the object is zero.Which force vector best represents the third force?}

A)(1)
B)(2)
C)(3)
D)(4)
E)none of the vectors

Answer 1

(4)

Question 2

A net force of 64 N acts on a mass of 16 kg.The resulting acceleration is

A)16 m/s²
B)0.51 m/s²
C)64 m/s²
D)9.0 m/s²
E)4.0 m/s²

Answer 2

4.0 m/s²

Question 3

An inertial reference frame is one in which

A)Newton's first law describes the behavior of matter.
B)the law of inertia is not applicable.
C)there is a great deal of matter.
D)the object of interest is traveling in a circular path.
E)forces do not necessarily exist in pairs.

Answer 3

Newton's first law describes the behavior of matter.

Question 4

Which fundamental force holds the atoms together in a block of wood?

A)gravitational force
B)electromagnetic force
C)weak nuclear force
D)strong nuclear force
E)all the four forces

Question 5

A force F produces an acceleration a on an object of mass m.A force 3F is exerted on a second object,and an acceleration 8a results.What is the mass of the second object?

A)3m
B)9m
C)24m
D)(3/8)m
E)(8/3)m

Question 6

An object is moving to the right at a constant speed.Which one of the following statements must be correct?

A)No forces are acting on the object.
B)A larger number of forces are acting on the object to the right than to the left.
C)The net force acting on the object is to the right.
D)No net force is acting on the object.
E)Just one force is acting on the object,and it is acting downward.

Question 7

A 10-N force is applied to mass M.The same force is applied to mass 4M.The ratio of the acceleration of the smaller mass to the acceleration of the larger mass is

A)4 to 1
B)20 to 1
C)1 to 1
D)1 to 2
E)1 to 4

Question 8

Newton's law of inertia does not describe the behavior of objects

A)in inertial frames of reference.
B)moving with constant velocity relative to a given frame of reference.
C)at rest relative to a given frame of reference.
D)moving in accelerated frames of reference.
E)moving in a straight line at constant speed relative to a given reference frame.

Question 9

A physical quantity that is sometimes described as the measure of the resistance of a body to a change in motion is

A)force
B)mass
C)acceleration
D)weight
E)friction

Question 10

A force accelerates a body of mass M.The same force applied to a second body produces three times the acceleration.What is the mass of the second body?

A)M
B)3M
C)M/3
D)9M
E)M/9

Question 11

If you apply the same force to objects with masses M and 4M,the acceleration of the mass M is

A)the same as for the mass 4M.
B)four times the acceleration of the mass 4M.
C)one-fourth the acceleration of the mass 4M.
D)twice the acceleration of the mass 4M.
E)one-half the acceleration of the mass 4M.

Question 12

Which of the following statements includes all the essential elements of Newton's first law?

A)A body at rest persists in its state of rest unless acted on by a non-zero net external force.
B)A body persists in its state of rest or of uniform motion in a straight line as long as the net external force remains constant.
C)For every action there is an equal and opposite reaction.
D)A body persists in its state of rest or of uniform motion in a straight line unless acted on by a non-zero net external force.
E)The acceleration of a body is proportional to the net external force acting on it and to the mass of the body.

Question 13

A particle with a mass of 200 g is acted on by a force of 4.5 N.The acceleration of the particle is

A)90 cm/s²
B)2.3 cm/s²
C)0.90 km/s²
D)23 m/s²
E)9.0 m/s²

Question 14

According to Newton's law of inertia,

A)objects moving with an initial speed relative to a given frame of reference eventually come to rest relative to the reference frame.
B)whether an object is at rest or is moving with constant velocity depends on the inertial reference frame in which the object is observed.
C)rest is the most natural state of motion.
D)an object at rest in a given frame of reference eventually finds itself in motion relative to the frame of reference.
E)forces always exist in pairs.

Question 15

A force accelerates a body of mass M.A second body requires twice as much force to produce the same acceleration.What is the mass of the second body?

A)M
B)2M
C)M/2
D)4M
E)M/4

Question 16

A body moves with constant speed in a straight line.Which of the following statements must be true?

A)No force acts on the body.
B)A single constant force acts on the body in the direction of motion.
C)A single constant force acts on the body in the direction opposite to the motion.
D)A net force of zero acts on the body.
E)A constant net force acts on the body in the direction of motion.

Question 17

The figure below shows two forces,F_{1< / sub> and F2< / sub>,acting on an object. Use the vector diagrams to answer the question.
Which force vector best represents the resultant force on the object?}

A)(1)
B)(2)
C)(3)
D)(4)
E)none of the vectors

Question 18

A mass of 25 kg is acted on by two forces: ₁ is 15 N due east,and ₂ is 10 N due north.The acceleration of the mass is

A)0.72 m/s²,56.3º north of east.
B)0.20 m/s²,due east.
C)0.72 m/s²,33.7º north of east.
D)1.0 m/s²,33.7º north of east.
E)0.20 m/s²,56.3º north of east.

Question 19

When Newton's first law of motion is mentioned,you should immediately think of

A)
B)action-and-reaction forces.
C)inertia.
D)gravitational forces.
E)centripetal acceleration.

Question 20

A mass m is traveling at an initial speed v₀ = 25.0 m/s.It is brought to rest in a distance of 62.5 m by a force of 15.0 N.The mass is

A)37.5 kg
B)3.00 kg
C)1.50 kg
D)6.00 kg
E)3.75 kg

Question 21

The SI unit of force is the

A)newton
B)gram
C)pound
D)kilogram
E)None of these is correct.

Question 22

The mass of a body that weighs 2.00 N at sea level is

A)0.204 kg
B)2.00 kg
C)19.6 kg
D)9.80 kg
E)0.451 kg

Question 23

A fat cat,ever conscious of its weight,walks into an elevator and steps on a scale.The elevator begins to accelerate downward.While the elevator is accelerating,the scale reads

A)more than when the elevator is stationary.
B)more than if the elevator were accelerating upward.
C)less than when the elevator is stationary.
D)a negative value.
E)Insufficient information is given to answer correctly.

Question 24

An unknown force is applied to two unknown masses M_A and M_B.Their accelerations _A and _B are measured.From these data we can determine

A)the magnitude of only.
B)M_A and M_B only.
C)the magnitudes of ,M_A,and M_B only.
D)the ratio of M_A to M_B only.
E)M_A,M_B,and the weights of M_A and M_B.

Question 25

In the cgs system,the units of force are

A)g · cm
B)g · cm²/s²
C)g · cm/s²
D)g · s/cm
E)cm · s²

Question 26

A body is sent out in space.Which of the following statements is true of this body as it moves away from Earth?

A)The body's mass and weight remain equal.
B)The body's mass remains constant,and its weight decreases.
C)The body's mass decreases,and its weight remains constant.
D)The body's mass and weight decrease.
E)The body's mass decreases,and its weight increases.

Question 27

The diagrams below show the application of a force F on a block of mass m. Which diagram(s)produces the largest acceleration on the block in the horizontal direction?

A)(1)and (3)
B)(2)
C)(3)
D)(2)and (4)
E)The acceleration is the same for all four.

Question 28

A person of weight w is in an upward-moving elevator when the cable suddenly breaks.What is the person's apparent weight immediately after the elevator starts to fall?

A)w
B)greater than w
C)less than w
D)9.81w
E)zero

Question 29

A ball of mass 2.0 kg is acted on by two forces, and .The magnitude of the acceleration is

A)2.5 m/s²
B)3.9 m/s²
C)4.6 m/s²
D)5.1 m/s²
E)5.8 m/s²

Question 30

Which of the following statements is true?

A)The mass of a body is a quantitative measure of its inertia.
B)Mass is a vector quantity.
C)The mass of a body is directly proportional to the acceleration it is experiencing.
D)The unit of mass in the U.S.customary system is the newton.
E)The mass of a body is inversely proportional to the resultant force acting on it.

Question 31

The weight of an object is

A)the same as the mass of the object.
B)the quantity of matter in the object.
C)the mass of the object multiplied by the acceleration due to gravity at sea level,regardless of where the object is located.
D)the result of the gravitational force acting on the object.
E)the reading on a spring scale attached to the object.

Question 32

Rachel has been reading her physics book.She takes her weighing scales into an elevator and stands on them.If her normal weight is 690 N (155 lbs),and the elevator moves upward at 0.25g and then down at 0.25g,what is the difference between the up and down scale readings?

A)690 N
B)520 N
C)170 N
D)345 N
E)1.04 $\times$ 10³ N

Question 33

A shopper steps on an escalator moving downward at a constant speed toward the bargain basement in a large department store.On his way down,the normal force exerted on him by the step of the escalator is

A)greater than his weight when he is off the escalator.
B)equal to his weight when he is off the escalator.
C)less than his weight when he is off the escalator.
D)dependent on how fast the escalator is moving.
E)unknown; insufficient information is given to answer correctly.

Question 34

An astronaut lands on an Earthlike planet and drops a small lead ball with a mass of 76.5 g from the top of her spaceship.The point of release is 18 m above the surface of the planet and the ball takes 2.5 s to reach the ground.The astronaut's mass on Earth is 68.5 kg.Her weight on the planet is

A)69.0 N
B)395 N
C)670 N
D)990 N
E)1.02 kN

Question 35

A ball of mass 2.0 kg is acted on by two forces, and .At t = 0 s,the particle is at rest at the origin.The velocity vector at t = 2 s is

A)
B)
C)
D)
E)

Question 36

If force (in N),length (in m),and time (in s)were considered to be the fundamental quantities,the units of mass would be

A)s²/(N · m)
B)m · s
C)N² · m/s²
D)N · s²/m
E)m/N

Question 37

Which of the following is not a unit of force?

A)newton
B)pound
C)slug
D)dyne
E)kg · m/s²

Question 38

The acceleration due to gravity on the moon is only about 1/6 of that on Earth.An astronaut whose weight on Earth is 600 N travels to the lunar surface.His mass as measured on the moon is

A)600 kg
B)100 kg
C)61.2 kg
D)10.0 kg
E)360 kg

Question 39

A ball of mass 2.0 kg is acted on by two forces, and .At t = 0 s,the particle is at rest at the origin.The position vector at t = 2 s is

A)
B)
C)
D)
E)

Question 40

A ball of mass 2.0 kg is acted on by two forces, and .The acceleration vector of the mass is (in m/s²)

A)
B)
C)
D)
E)

Question 41

If a force F is required to extend a spring by 20 cm,what force is required to extend it by 30 cm?

A)F
B)(2/3)F
C)(3/2)F
D)600F
E)(3/5)F

Question 42

Which of the following is a unit of force?

A)m²/s²
B)kg · s²/m
C)kg · m/s²
D)N · s
E)N/kg

Question 43

We all know it makes sense to bend one's knees when dropping from a height. Suppose a very silly 70-kg person were instead to drop down from a height of 1.4 m onto the ground and stop stiffly within a distance of only 0.60 cm.Calculate how many times his own weight is the average force his body feels.

A)15
B)24
C)2.3 $\times$ 10³
D)6.1 $\times$ 10²
E)2.3 $\times$ 10²

Question 44

A horse-drawn coach is decelerating at 3.0 m/s² while moving in a straight line horizontally.A 350-g mass is hanging on a string 1.6 m long from the ceiling of the coach.The angle that the string makes with the vertical is

A)9.3º toward the front of the coach.
B)17º toward the front of the coach.
C)9.3º toward the back of the coach.
D)2.5º toward the front of the coach.
E)0º,or straight down.

Question 45

A book is placed on a flat horizontal table.The table exerts a normal force on the book.The origin of the normal force in terms of the fundamental forces is

A)gravitational force.
B)electromagnetic force.
C)weak nuclear force
D)strong nuclear force
E)all the four forces

Question 46

A lamp with a mass m is suspended from the ceiling by two cords as shown.The ratio of the magnitude of the vertical component of the tension in ₂ to that in ₃ is

A)1:1
B)1:2
C)
D)3:2
E)3:1

Question 47

You are going up in an elevator that is accelerating upwards on Earth.Suppose you were to do the same thing on Mars.Your weight on Mars will be ___ your weight on Earth.

A)less than
B)equal to
C)greater than
D)unable to tell
E)depends on what g is on Mars

Question 48

What is the weight of a 50-kg boy on the moon,where the acceleration due to gravity is 1.6 m/s²?

A)80 N
B)100 N
C)490 N
D)50 N
E)80 lb

Question 49

Of the following values,which is most nearly equal to the weight of a 1-kg body?

A)1 N
B)103 dynes
C)2.2 lb
D)0.454 lb
E)2.2 N

Question 50

A lamp with a mass m = 42.6 kg is hanging from wires as shown.The tension ₁ in the vertical wire is

A)210 N
B)417 N
C)570 N
D)360 N
E)730 N

Question 51

Spiral springs A and B are identical.When a weight of 12 N is fastened to the hook on A,the hook is lowered 2 cm.If a weight of 18 N is fastened to the hook on B,that hook is lowered

A)8 cm
B)6 cm
C)3 cm
D)4 cm
E)5 cm

Question 52

The concept of a field

A)provides us with a way to understand how a body's presence is known over great distances.
B)is a useful alternative to action at a distance for explaining gravitational forces.
C)is that of space distorted by the presence of an object.
D)is useful in describing electromagnetic interactions as well as gravitational interactions.
E)is described by all of these.

Question 53

A net force is exerted toward the east on an object that is initially at rest.In which direction does the object start to move?

A)north
B)east
C)west
D)south
E)It may start to move in any of these directions.

Question 54

In a crash test the strapped-in,75-kg dummy moves a distance of 0.80 m when the test car is slammed straight into a wall at 11.2 m/s (~25 mph).The average force acting on the dummy during the collision is how many times his own weight?

A)0.13
B)78
C)0.71
D)8.0
E)4.0

Question 55

A 44.5-N weight is hung on a spring scale,and the scale is hung on a string.The string is lowered at a rate such that the entire assembly has a downward acceleration of 4.90 m/s².The scale reads

A)0 N
B)22.2 N
C)44.5 N
D)66.7 N
E)71.2 N

Question 56

The force needed to accelerate "Opportunity" (Opportunity is a Mars rover)on Mars at 1 m/s² in the horizontal direction is ____ the force needed to accelerate the rover while it was undergoing testing on Earth.

A)less than
B)equal to
C)greater than
D)unable to tell
E)depends on what g is on Mars

Question 57

Which of the following is not a unit of mass?

A)pound
B)kilogram
C)gram
D)slug
E)milligram

Question 58

The system in the figure consists of a steel ball attached by a cord to a large block of wood.If the system is dropped in a vacuum,the force in the cord is

A)zero.
B)equal to the difference of the masses of B and W.
C)equal to the difference of the weights of B and W.
D)equal to the weight of B.
E)equal to the sum of the weights of B and W.

Question 59

A car is accelerating at a rate of 2.5 m/s².A mass of 250 g is hanging from the ceiling on a string 1.2 m long.The angle that the string makes with the vertical is

A)14.3º toward the back of the car.
B)76º toward the back of the car.
C)7º toward the front of the car.
D)14.3º toward the front of the car.
E)0º,or straight down.

Question 60

If a force F is required to extend a spring a distance 5y,how far will it be extended by force 3F?

A)5y
B)(3/5)y
C)(5/3)y
D)15y
E)(3/8)y

Question 61

A vertical rope is attached to an object that has a mass of 40.0 kg and is at rest.The tension in the rope needed to give the object an upward speed of 3.50 m/s in 0.700 s is

A)592 N
B)390 N
C)200 N
D)980 N
E)720 N

Question 62

You want to elope by sliding down a nylon rope made by tying stockings together.The rope will withstand a maximum tension of 300 N without breaking.Your mass is 61.2 kg.The magnitude of the smallest acceleration a with which you can slide down the rope is

A)9.81 m/s²
B)4.91 m/s²
C)zero
D)2.40 m/s²
E)19.6 m/s²

Question 63

A particle of mass 1.3 kg is sliding down a frictionless slope inclined at 30º to the horizontal.The acceleration of the particle down the slope is

A)1.3 m/s²
B)9.8 m/s²
C)0.5 m/s²
D)8.5 m/s²
E)4.9 m/s²

Question 64

A particle has a mass of 6.0 $\times$ 10^-6 kg and a velocity of 800 m/s along the x axis when a force of 14.4 $\times$ 10^-5 N along the y axis acts on the particle at right angles to its velocity.The acceleration of the particle is

A)24 m/s² along the x axis.
B)zero.
C)impossible to determine; forces never act at right angles to velocities.
D)24 m/s² along the y axis.
E)tangential.

Question 65

A force of 3.0 N acts on a body along a direction 30º above the horizontal.In addition,there is a gravitational force of 4.0 N downward.The resultant force has a magnitude of

A)7.0 N
B)6.8 N
C)6.1 N
D)3.6 N
E)5.0 N

Question 66

Three forces F₁,F₂ and F₃ act on an object.If F₁ = 3N i + 5N j + 7N k,F₂ = -5N i - 2N j -2N k,and the object is moving at constant velocity then the vector force F₃ is

A)-2N i - 3N j - 5N k
B)2N i - 3N j - 5N k
C)2N i + 3N j - 5N k
D)-8N i - 7N j - 9N k
E)8N i + 7 N j +9N k

Question 67

Your heart pumps 80 g of blood with each beat.The blood starts from rest and reaches a speed of 0.60 m/s in the aorta.If each beat takes 0.16 s,the average force exerted on the blood is

A)3.0 $\times$ 10² N
B)0.22 N
C)0.16 N
D)0.30 N
E)0.98 N

Question 68

A bell hangs from a blue rope.A red rope attached to the side of the bell is pulled in the horizontal direction.This causes the blue rope to make an angle less than 90º with the vertical.Which of the following statements is true?

A)The red rope is under greater tension than the blue rope.
B)The red rope is under the same tension as the blue rope.
C)The blue rope is under greater tension than the red rope.
D)The tensions cannot be compared unless the mass of the bell is known.
E)The tensions cannot be compared unless the angle that the blue rope makes with the vertical is known.

Question 69

Three forces, , ,and ,act on a mass of 4.2 kg.The forces are The direction of the net acceleration

A)cannot be determined because the acceleration is zero.
B)is 60º north of east.
C)is 70º north of east.
D)is 51º north of east.
E)is 44º north of east.

Question 70

A lamp of mass m hangs from a spring scale that is attached to the ceiling of an elevator.When the elevator is stopped at the fortieth floor,the scale reads mg.What does it read while the elevator descends toward the ground floor at a constant speed?

A)more than mg
B)less than mg
C)mg
D)zero
E)This cannot be answered without knowing how fast the elevator is descending.

Question 71

A lamp of mass m hangs from a spring scale which is attached to the ceiling of an elevator.When the elevator is stopped at the fortieth floor,the scale reads mg.What does it read as the elevator slows down to stop at the ground floor?

A)more than mg
B)less than mg
C)mg
D)zero
E)One cannot tell without knowing how fast the elevator is stopping.

Question 72

A box sits on an inclined plane without sliding.As the angle of inclination increases,the normal force

A)increases.
B)decreases.
C)does not change.
D)is directed upward.
E)is directed in the direction of the gravitational force.

Question 73

A boy holds a bird in his hand.The reaction force to the normal force exerted on the bird by the boy's hand is the force of:

A)the Earth on the bird.
B)the bird on the Earth.
C)the hand on the bird.
D)the bird on the hand.
E)the Earth on the hand.

Question 74

Three forces, , ,and ,act on a mass of 4.2 kg.The forces are The magnitude of the net acceleration of the mass is

A)2.9 m/s²
B)5.3 m/s²
C)1.4 m/s²
D)0.0 m/s²
E)18 m/s²

Question 75

A net force is exerted on an object toward the north.The object

A)is moving toward the north.
B)is moving toward the east.
C)is moving toward the west.
D)is moving toward the south.
E)may be moving in any direction.

Question 76

An 80-kg man on ice skates pushes a 40-kg boy,also on skates,with a force of 100 N.The force exerted by the boy on the man is

A)200 N
B)100 N
C)50 N
D)40 N
E)zero unless the boy pushes back

Question 77

A lamp of mass m hangs from a spring scale that is attached to the ceiling of an elevator.When the elevator is stopped at the fortieth floor,the scale reads mg.What does it read as the elevator slows down to stop at the forty-fifth floor?

A)more than mg
B)less than mg
C)mg
D)zero
E)One cannot tell without knowing how fast the elevator is stopping.

Question 78

A boy sits in a tire that is attached to a rope that passes over a pulley fastened to the ceiling and then passes back down to the boy's hands.The weight of the boy plus the tire is W.The force with which the boy must pull on the free end of the rope to support his weight in the tire is

A)(1/2)W
B)W
C)2W
D)(2/3)W
E)(3/2)W

Question 79

A man riding in an elevator has an apparent weight greater than his actual weight.Which one of the following statements could be true?

A)The elevator moves upward with constant speed.
B)The elevator moves downward with constant speed.
C)The elevator moves upward with decreasing speed.
D)The elevator moves downward with decreasing speed.
E)The elevator moves downward with increasing speed.

Question 80

The word "normal," as it applies to forces,means

A)usual.
B)mean.
C)average.
D)perpendicular.
E)straight up,in the direction opposite to the force of gravity.