Deck 5: The Laws of Motion

Question 1

If F = 4.0 N and m = 2.0 kg,what is the magnitude a of the acceleration for the block shown below? The surface is frictionless.

A)5.3 m/s²
B)4.4 m/s²
C)3.5 m/s²
D)6.2 m/s²
E)8.4 m/s²

Answer 1

3.5 m/s²

Question 2

If α = 40°,β = 60°,and M = 4.0 kg,determine the tension in string 1.

A)15 N
B)22 N
C)17 N
D)20 N
E)36 N

Answer 2

20 N

Question 3

If M = 6.0 kg,what is the tension in string 1?

A)39 N
B)34 N
C)29 N
D)44 N
E)51 N

Answer 3

51 N

Question 4

The only two forces acting on a body have magnitudes of 20 N and 35 N and directions that differ by 80°.The resulting acceleration has a magnitude of 20 m/s².What is the mass of the body?

A)2.4 kg
B)2.2 kg
C)2.7 kg
D)3.1 kg
E)1.5 kg

Question 5

In the figure,if the tension in string 1 is 34 N and the tension in string 2 is 24 N,what is the mass of the object shown?
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A)7.3 kg
B)5.5 kg
C)1.8 kg
D)3.7 kg
E)4.5 kg

Question 6

Two forces are the only forces acting on a 3.0-kg object which moves with an acceleration of 3.0 m/s² in the positive y direction.If one of the forces acts in the positive x direction and has a magnitude of 8.0 N,what is the magnitude of the other force?

A)12 N
B)14 N
C)16 N
D)18 N
E)22 N

Question 7

If α = 40° and the tension in string 2 is 30 N,determine M.

A)3.4 kg
B)3.6 kg
C)2.6 kg
D)4.9 kg
E)7.5 kg

Question 8

A 5.0-kg mass is attached to the ceiling of an elevator by a rope whose mass is negligible.What force does the mass exert on the rope when the elevator has an acceleration of 4.0 m/s² upward?

A)69 N downward
B)29 N downward
C)49 N downward
D)20 N downward
E)19 N downward

Question 9

The tension in a string from which a 4.0-kg object is suspended in an elevator is equal to 44 N.What is the acceleration of the elevator?

A)11 m/s² upward
B)1.2 m/s² upward
C)1.2 m/s² downward
D)10 m/s² upward
E)2.4 m/s² downward

Question 10

An object of unknown weight is suspended as shown.The tension in rope 1 is 25 lb,and the tension in rope 2 is 31 lb.What is the weight of the suspended object?

A)36 lb
B)33 lb
C)41 lb
D)39 lb
E)56 lb

Question 11

A 3.0-kg block slides on a frictionless 20° inclined plane.A force of 16 N acting parallel to the incline and up the incline is applied to the block.What is the acceleration of the block?

A)2.0 m/s² down the incline
B)5.3 m/s² up the incline
C)2.0 m/s² up the incline
D)3.9 m/s² down the incline
E)3.9 m/s² up the incline

Question 12

At an instant when a 4.0-kg object has an acceleration equal to
M/s²,one of the two forces acting on the object is known to be
n.Determine the magnitude of the other force acting on the object.

A)2.0 N
B)13 N
C)18 N
D)1.7 N
E)20 N

Question 13

A block is pushed up a frictionless 30° incline by an applied force as shown.If F = 25 N and M = 3.0 kg,what is the magnitude of the resulting acceleration of the block?

A)2.3 m/s²
B)4.6 m/s²
C)3.5 m/s²
D)2.9 m/s²
E)5.1 m/s²

Question 14

A 5.0-kg mass is suspended by a string from the ceiling of an elevator that is moving upward with a speed which is decreasing at a constant rate of 2.0 m/s in each second.What is the tension in the string supporting the mass?

A)49 N
B)39 N
C)59 N
D)10 N
E)42 N

Question 15

If M = 1.1 kg,what is the tension in string 1?

A)54 N
B)47 N
C)40 N
D)62 N
E)57 N

Question 16

The horizontal surface on which the block slides is frictionless.If F = 20 N and M = 5.0 kg,what is the magnitude of the resulting acceleration of the block?

A)5.3 m/s²
B)6.2 m/s²
C)7.5 m/s²
D)4.7 m/s²
E)3.2 m/s²

Question 17

If the only forces acting on a 2.0-kg mass are
N and
N,what is the magnitude of the acceleration of the particle?

A)1.5 m/s²
B)6.5 m/s²
C)4.7 m/s²
D)9.4 m/s²
E)7.2 m/s²

Question 18

A person weighing 0.70 kN rides in an elevator that has an upward acceleration of 1.5 m/s².What is the magnitude of the force of the elevator floor on the person?

A)0.11 kN
B)0.81 kN
C)0.70 kN
D)0.59 kN
E)0.64 kN

Question 19

If M = 2.0 kg,what is the tension in string 1?

A)1.2 N
B)11 N
C)34 N
D)3.5 N
E)40 N

Question 20

A 5.0-kg object is suspended by a string from the ceiling of an elevator that is accelerating downward at a rate of 2.6 m/s².What is the tension in the string?

A)49 N
B)36 N
C)62 N
D)13 N
E)52 N

Question 21

When the vector sum of three co-planar forces,
,
And
,is parallel to
,we can conclude that
And

A)must sum to zero.
B)must be equal and opposite.
C)must have equal and opposite components perpendicular to .
D)must have equal and opposite components parallel to .
E)must have equal and opposite components parallel and perpendicular to .

Question 22

A constant force is applied to a body that is already moving.The force is directed at an angle of 60 degrees to the direction of the body's velocity.What is most likely to happen is that

A)the body will stop moving.
B)the body will move in the direction of the force.
C)the body's velocity will increase in magnitude but not change direction.
D)the body will gradually change direction more and more toward that of the force while speeding up.
E)the body will first stop moving and then move in the direction of the force.

Question 23

The first of two identical boxes of mass m is sitting on level ground.The second box is sitting on a ramp that makes a 20° angle with the ground.The normal force of the level ground on the first box is N_L;the normal force of the ramp on the second box is N_R.Which statement is correct?

A)N_R = N_L = mg.
B)N_L = mg;N_R = mg sin 20°.
C)N_L = mg;N_R = mg cos 20°.
D)N_L = mg;N_R = −mg cos 20°.
E)N_R = −N_L = −mg.

Question 24

A 1.5-kg object has a velocity of 5
M/s at t = 0.It is accelerated at a constant rate for five seconds after which it has a velocity of (6
+ 12
)m/s.What is the magnitude of the resultant force acting on the object during this time interval?

A)3.8 N
B)3.2 N
C)2.8 N
D)4.3 N
E)4.6 N

Question 25

The apparent weight of a fish in an elevator is greatest when the elevator

A)moves downward at constant velocity.
B)moves upward at constant velocity.
C)accelerates downward.
D)accelerates upward.
E)is not moving.

Question 26

The vector sum of three co-planar forces

A)must be zero.
B)must be perpendicular to one of the three.
C)must be parallel to one of the three.
D)must be perpendicular to the plane.
E)may have any direction in the plane.

Question 27

A constant force F is applied to a body of mass m that initially is headed east at velocity v₀ until its velocity becomes −v₀.The total time of travel is 2t.The total distance the body travels in that time is

A) .
B) .
C) .
D) .
E) .

Question 28

A juggler throws two balls up to the same height so that they pass each other halfway up when A is rising and B is descending.Ignore air resistance and buoyant forces.Which statement is true of the two balls at that point?

A)There is an residual upward force from the hand on each ball.
B)There is a greater residual force from the hand on A than there is on B.
C)Only gravity acts on B but there is an additional residual force from the hand on A.
D)There is an additional downwards force besides gravity on each ball.
E)The only force acting on each ball is the gravitational force.

Question 29

The first of two identical boxes of mass m is sitting on level ground.The second box is sitting on a ramp that makes an angle with the ground.When a force of magnitude F is applied to each box in a direction parallel to the surface it is on,upwards on the box on the ramp,neither box moves.Which statement comparing the friction force on the box on the level,f_L,to the friction force on the box on the ramp,f_R,is correct?

A)f_R = f_L.
B)f_R > f_L.
C)f_R < f_L.
D)The coefficient of static friction is needed to determine the correct answer.
E)Depending on the values of the coefficient of static friction,the angle of elevation of the ramp,the mass of the boxes,and the applied force,answers (a), (b),and (c)are each a possible correct answer.

Question 30

A book is placed on a chair.Then a videocassette is placed on the book.The floor exerts a normal force

A)on all three.
B)only on the book.
C)only on the chair.
D)upwards on the chair and downwards on the book.
E)only on the objects that you have defined to be part of the system.

Question 31

The total force needed to drag a box at constant speed across a surface with coefficient of kinetic friction μ_k is least when the force is applied at an angle θ such that

A)sinθ = μ_k.
B)cosθ = μ_k.
C)tanθ = μ_k.
D)cotθ = μ_k.
E)secθ = μ_k.

Question 32

Only two forces act on a 3.0-kg mass.One of the forces is 9.0 N east,and the other is 8.0 N in the direction of 62° north of west.What is the magnitude of the acceleration of the mass?

A)2.0 m/s²
B)2.4 m/s²
C)3.3 m/s²
D)2.9 m/s²
E)5.7 m/s²

Question 33

A 1.5-kg mass has an acceleration of (4.0
− 3)0
)m/s².Only two forces act on the mass.If one of the forces is (2.0
− 1)4
)N,what is the magnitude of the other force?

A)4.1 N
B)6.1 N
C)5.1 N
D)7.1 N
E)2.4 N

Question 34

You have a machine which can accelerate pucks on frictionless ice.Starting from rest,the puck travels a distance x in time t when force F is applied.If force 3F is applied,the distance the puck travels in time t is

A)x.
B)(3/2)x.
C)3x.
D)(9/2)x.
E)9x.

Question 35

A 2.0-kg block slides on a frictionless 25° inclined plane.A force of 4.6 N acting parallel to the incline and up the incline is applied to the block.What is the acceleration of the block?

A)1.8 m/s² up the incline
B)2.3 m/s² up the incline
C)6.6 m/s² down the incline
D)1.8 m/s² down the incline
E)2.3 m/s² down the incline

Question 36

A 2.0-kg object has a velocity of 4.0
M/s at t = 0.A constant resultant force of (2.0
+ 4)0
)N then acts on the object for 3.0 s.What is the magnitude of the object's velocity at the end of the 3.0-s interval?

A)9.2 m/s
B)6.3 m/s
C)8.2 m/s
D)7.2 m/s
E)7.7 m/s

Question 37

A 2.0-kg block slides on a frictionless 15° inclined plane.A force acting parallel to the incline is applied to the block.The acceleration of the block is 1.5 m/s² down the incline.What is the applied force?

A)8.1 N down the incline
B)3.0 N down the incline
C)2.1 N up the incline
D)3.0 N up the incline
E)8.1 N up the incline

Question 38

A 1.5-kg object has a velocity of 5
M/s at t = 0.It is accelerated at a constant rate for five seconds after which it has a velocity of (6
+ 12
)m/s.What is the direction of the resultant force acting on the object during this time interval?

A)65°
B)56°
C)61°
D)49°
E)27°

Question 39

A heavy weight is supported by two cables that exert tensions of magnitude T₁ and T₂.Which statement is correct?

A)T₁ = T₂.
B)T_1y = T_2y.
C)T₁ > T₂.
D)T₁ < T₂.
E)We need the mass of the box in order to determine the correct answer.

Question 40

A bumper car is moving at constant velocity when another bumper car starts to push on it with a constant force at an angle of 60 degrees with respect to the first car's initial velocity.The second bumper car continues pushing in exactly that direction for some time.What is most likely to happen is that

A)the first car will stop moving.
B)the first car will move in the direction of the force.
C)the first car's velocity will increase in magnitude but not change direction.
D)the first car's velocity will gradually change direction more and more toward that of the force while increasing in magnitude.
E)the first car's velocity will gradually change direction more and more toward that of the force while decreasing in magnitude.

Question 41

If F = 40 N and M = 1.5 kg,what is the tension in the string connecting M and 2M? Assume that all surfaces are frictionless.

A)13 N
B)23 N
C)36 N
D)15 N
E)28 N

Question 42

Two people,each of 70 kg mass,are riding in an elevator.One is standing on the floor.The other is hanging on a rope suspended from the ceiling.Compare the acceleration
Of the first person to the acceleration
Of the second person.Which statement is correct?

A)They are equal and opposite in direction.
B)They are equal and have the same direction.
C)The acceleration is greater than ,but they have the same direction.
D)The acceleration is greater than ,but they have opposite directions.
E)The acceleration is less than ,but they have the same direction.

Question 43

An 8.0-kg object rests on the floor of an elevator which is accelerating downward at a rate of 1.3 m/s².What is the magnitude of the force the object exerts on the floor of the elevator?

A)59 N
B)10 N
C)89 N
D)68 N
E)78 N

Question 44

A 6.0-kg object is suspended by a vertical string from the ceiling of an elevator which is accelerating upward at a rate of 1.8 m/s².Determine the tension in the string.

A)11 N
B)70 N
C)48 N
D)59 N
E)62 N

Question 45

The horizontal surface on which the objects slide is frictionless.If F = 12 N,what is the tension in string 1?

A)35 N
B)30 N
C)40 N
D)45 N
E)25 N

Question 46

A 5.0-kg mass sits on the floor of an elevator that has a downward acceleration of 1.0 m/s².On top of the 5.0-kg mass is an object of unknown mass.The force of the elevator on the 5.0-kg mass is 80 N up.Determine the unknown mass.

A)3.3 kg
B)2.4 kg
C)1.6 kg
D)4.1 kg
E)5.0 kg

Question 47

Two people,each of 70 kg mass,are riding in an elevator.One is standing on the floor.The other is hanging on a rope suspended from the ceiling.Compare the force
The floor exerts on the first person to the force
The rope exerts on the second person.Which statement is correct?

A)They are equal and opposite in direction.
B)They are equal and have the same direction.
C) is greater than ,but they have the same direction.
D) is greater than ,but they have opposite directions.
E) is less than ,but they have the same direction.

Question 48

An astronaut who weighs 800 N on the surface of the earth lifts off from planet Zuton in a space ship.The free-fall acceleration on Zuton is 3.0 m/s² (down).At the moment of liftoff the acceleration of the space ship is 0.50 m/s² (up).What is the magnitude of the force of the space ship on the astronaut?

A)41 N
B)0.29 kN
C)0.24 kN
D)0.20 kN
E)0.37 kN

Question 49

The horizontal surface on which the objects slide is frictionless.If F = 6.0 N and M = 1.0 kg,what is the magnitude of the force exerted on the large block by the small block?

A)7.7 N
B)9.8 N
C)9.1 N
D)8.4 N
E)6.5 N

Question 50

The surface of the inclined plane shown is frictionless.If F = 30 N,what is the magnitude of the force exerted on the 3.0-kg block by the 2.0-kg block?

A)18 N
B)27 N
C)24 N
D)21 N
E)15 N

Question 51

The system shown is released from rest and moves 50 cm in 1.0 s.What is the value of M? All surfaces are frictionless.

A)0.42 kg
B)0.34 kg
C)0.50 kg
D)0.59 kg
E)0.68 kg

Question 52

If M = 2.2 kg,what is the tension in the connecting string? The pulley and all surfaces are frictionless.

A)6.4 N
B)5.9 N
C)5.4 N
D)6.9 N
E)8.3 N

Question 53

A 70-kg stunt artist rides in a rocket sled which slides along a flat inclined surface.At an instant when the sled's acceleration has a horizontal component of 6.0 m/s² and a downward component of 2.8 m/s²,what is the magnitude of the force on the rider by the sled?

A)0.83 kN
B)0.98 kN
C)0.65 kN
D)0.68 kN
E)0.72 kN

Question 54

If F = 5.0 N,what is the magnitude of the force exerted by block 2 on block 1?

A)17 N
B)19 N
C)21 N
D)23 N
E)5.0 N

Question 55

The horizontal surface on which the objects slide is frictionless.If M = 2.0 kg,the tension in string 1 is 12 N.Determine F.

A)25 N
B)20 N
C)30 N
D)35 N
E)40 N

Question 56

If the tension,T,is 15 N and the magnitude of the acceleration,a,is 3.0 m/s²,what is the mass,m,of the suspended object? Assume that all surfaces and the pulley are frictionless.

A)3.1 kg
B)2.5 kg
C)2.8 kg
D)2.2 kg
E)3.7 kg

Question 57

If F = 40 N and M = 2.0 kg,what is the magnitude of the acceleration of the suspended object? All surfaces are frictionless.

A)1.2 m/s²
B)2.0 m/s²
C)1.5 m/s²
D)2.5 m/s²
E)5.6 m/s²

Question 58

If P = 6.0 N,what is the magnitude of the force exerted on block 1 by block 2?

A)6.4 N
B)5.6 N
C)4.8 N
D)7.2 N
E)8.4 N

Question 59

If F = 8.0 N and M = 1.0 kg,what is the tension in the connecting string? The pulley and all surfaces are frictionless.

A)4.1 N
B)3.5 N
C)3.8 N
D)3.1 N
E)4.8 N

Question 60

The horizontal surface on which the objects slide is frictionless.If M = 1.0 kg and the magnitude of the force of the small block on the large block is 5.2 N,determine F.

A)6.0 N
B)9.0 N
C)7.8 N
D)4.8 N
E)4.1 N

Question 61

Two blocks are accelerated across a horizontal frictionless surface as shown.Frictional forces keep the two blocks from sliding relative to each other,and the two move with the same acceleration.If F = 1.2 N and M = 1.0 kg,what is the horizontal component (frictional force)of the force of the large block on the small block?

A)0.40 N to the left
B)0.80 N to the right
C)0.40 N to the right
D)0.80 N to the left
E)1.20 N to the left

Question 62

A 3.0-kg block slides on a rough horizontal surface.A force of 8.0 N acting parallel to the surface is applied to the block.The coefficient of kinetic friction between the block and the surface is 0.15.What is the magnitude of the block's acceleration?

A)1.9 m/s²
B)1.2 m/s²
C)2.3 m/s²
D)1.5 m/s²
E)2.9 m/s²

Question 63

In a game of shuffleboard (played on a horizontal surface),a puck is given an initial speed of 6.0 m/s.It slides a distance of 9.0 m before coming to rest.What is the coefficient of kinetic friction between the puck and the surface?

A)0.20
B)0.18
C)0.15
D)0.13
E)0.27

Question 64

A 1.8-kg block is projected up a rough 10° inclined plane.As the block slides up the incline,its acceleration is 3.8 m/s² down the incline.What is the magnitude of the force of friction acting on the block?

A)5.0 N
B)3.8 N
C)4.2 N
D)4.6 N
E)6.5 N

Question 65

In the figure shown,the coefficient of kinetic friction between the block and the incline is 0.40.What is the magnitude of the acceleration of the suspended block as it falls? Disregard any pulley mass or friction in the pulley.

A)3.4 m/s²
B)3.7 m/s²
C)4.2 m/s²
D)3.9 m/s²
E)5.4 m/s²

Question 66

A 1.8-kg block is released from rest at the top of a rough 30° inclined plane.As the block slides down the incline,its acceleration is 3.0 m/s² down the incline.Determine the magnitude of the force of friction acting on the block.

A)4.2 N
B)3.0 N
C)3.4 N
D)3.8 N
E)2.3 N

Question 67

In the figure shown,the coefficient of kinetic friction between the block and the incline is 0.29.What is the magnitude of the acceleration of the suspended block as it falls? Disregard any pulley mass or friction in the pulley.

A)5.4 m/s²
B)5.2 m/s²
C)4.9 m/s²
D)5.6 m/s²
E)7.9 m/s²

Question 68

A 2.0-kg block slides on a rough horizontal surface.A force (P = 6.0 N)is applied to the block as shown.The magnitude of the block's acceleration is 1.2 m/s².What is the magnitude of the force of friction acting on the block?

A)2.0 N
B)1.4 N
C)1.6 N
D)2.8 N
E)3.4 N

Question 69

A box rests on the (horizontal)back of a truck.The coefficient of static friction between the box and the surface on which it rests is 0.24.What maximum distance can the truck travel (starting from rest and moving horizontally with constant acceleration)in 3.0 s without having the box slide?

A)14 m
B)11 m
C)19 m
D)24 m
E)29 m

Question 70

A block is pushed across a horizontal surface by the force shown.If the coefficient of kinetic friction between the block and the surface is 0.30,F = 20 N,θ = 30°,and M = 3.0 kg,what is the magnitude of the acceleration of the block?

A)2.8 m/s²
B)2.3 m/s²
C)1.8 m/s²
D)3.3 m/s²
E)5.4 m/s²

Question 71

In the figure,if F = 2.0 N and M = 1.0 kg,what is the tension in the connecting string? The pulley and all surfaces are frictionless.

A)2.6 N
B)1.1 N
C)2.1 N
D)1.6 N
E)3.7 N

Question 72

The block shown is pulled across the horizontal surface at a constant speed by the force shown.If M = 5.0 kg,F = 14 N and θ = 35°,what is the coefficient of kinetic friction between the block and the horizontal surface?

A)0.44
B)0.33
C)0.38
D)0.28
E)0.17

Question 73

The coefficient of kinetic friction between the surface and the larger block is 0.25,and the coefficient of kinetic friction between the surface and the smaller block is 0.40.If F = 22N and M = 1.0 kg in the figure,what is the magnitude of the acceleration of either block?

A)1.8 m/s²
B)2.6 m/s²
C)1.4 m/s²
D)2.2 m/s²
E)3.7 m/s²

Question 74

A 1.0-kg block is pushed up a rough 22° inclined plane by a force of 7.0 N acting parallel to the incline.The acceleration of the block is 1.4 m/s² up the incline.Determine the magnitude of the force of friction acting on the block.

A)1.9 N
B)2.2 N
C)1.3 N
D)1.6 N
E)3.3 N

Question 75

A 3.0-kg block moves up a 40° incline with constant speed under the action of a 26-N force acting up and parallel to the incline.What magnitude force must act up and parallel to the incline for the block to move down the incline at constant velocity?

A)14 N
B)12 N
C)16 N
D)18 N
E)25 N

Question 76

The three blocks shown are released from rest and are observed to move with accelerations that have a magnitude of 1.5 m/s².What is the magnitude of the friction force on the block that slides horizontally? Disregard any pulley mass or friction in the pulley and let M = 2.0 kg.

A)6.0 N
B)5.1 N
C)5.5 N
D)4.6 N
E)3.7 N

Question 77

Two blocks in contact with each other are pushed to the right across a rough horizontal surface by the two forces shown.If the coefficient of kinetic friction between each of the blocks and the surface is 0.30,determine the magnitude of the force exerted on the 2.0-kg block by the 3.0-kg block.

A)15 N
B)25 N
C)11 N
D)22 N
E)33 N

Question 78

A 2.0-kg block slides on a rough horizontal surface.A force (magnitude P = 4.0 N)acting parallel to the surface is applied to the block.The magnitude of the block's acceleration is 1.2 m/s².If P is increased to 5.0 N,determine the magnitude of the block's acceleration.

A)2.1 m/s²
B)2.3 m/s²
C)1.9 m/s²
D)1.7 m/s²
E)3.2 m/s²

Question 79

A 4.0-kg block slides down a 35° incline at a constant speed when a 16-N force is applied acting up and parallel to the incline.What is the coefficient of kinetic friction between the block and the surface of the incline?

A)0.20
B)0.23
C)0.26
D)0.33
E)0.41

Question 80

A 4.0-kg block is pushed up a 36° incline by a force of magnitude P applied parallel to the incline.When P is 31 N,it is observed that the block moves up the incline with a constant speed.What value of P would be required to lower the block down the incline at a constant speed?

A)27 N
B)15 N
C)13 N
D)17 N
E)19 N