Deck 6: Applications of Newtons Laws

Question 1

The Moon is accelerated toward the earth,so it is gradually getting closer to the earth.

Answer 1

False

Question 2

When a car goes around a banked circular curve at the proper speed speed for the banking angle,what force cause it to follow the circular path?

A)the normal force from the road
B)the friction force from the road
C)gravity
D)No force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration.

Answer 2

the normal force from the road

Question 3

An object moves in a circular path at a constant speed.Compare the direction of the object's velocity and acceleration vectors.

A)Both vectors point in the same direction.
B)The vectors point in opposite directions.
C)The vectors are perpendicular to each other.
D)The acceleration is zero but the velocity is constant.

Answer 3

The vectors are perpendicular to each other.

Question 4

Three boxes are pulled along a horizontal frictionless floor by a constant horizontal pull P.The boxes are connected by very light horizontal strings having tensions T₁ and T₂ as shown in the figure.Which of the following statements about the tensions is correct? (There could be more than one correct choice. )

A)T₁ = P
B)T₂ = P
C)T₁ + T₂ = P
D)T₂ > T₁
E)T₁ > T₂

Question 5

In the figure,what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

A)exactly 2.0 N.
B)exactly 1.0 N
C)0.50 N
D)0.00 N
E)more than 19.6 N

Question 6

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same.
Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the lower block,B?

A)

B)

C)

D)

E)None of these diagrams is correct.

Question 7

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The normal force on the box due to the floor is equal to

A)W.
B)W + P.
C)W + P cos θ.
D)W + P sin θ.
E)W - P sin θ.

Question 8

As shown in the figure,a woman is straining to lift a large crate,but without success because it is too heavy.We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person,C is the magnitude of the vertical contact force on the crate by the floor,and W is the weight of the crate.How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

A)P + C = W
B)P + C < W
C)P + C > W
D)P = C

Question 9

Two cars go around a banked curve at the proper speed for the banking angle.One car has tires with excellent traction,while the other car has bald slippery tires.Which of these cars is more likely to slide on the pavement as it goes around the curve?

A)the car with the new tires
B)the car with the bald tires
C)Neither car will slide.
D)It depends on if the pavement is wet or dry.

Question 10

When an object moves in uniform circular motion,the direction of its acceleration is

A)in the same direction as its velocity vector.
B)in the opposite direction of its velocity vector.
C)is directed toward the center of its circular path.
D)is directed away from the center of its circular path.
E)depends on the speed of the object.

Question 11

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same.
Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block,A?

A)

B)

C)

D)

E)

Question 12

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord.The mass of P is greater than that of Q.A horizontal force
Is applied to box Q as shown in the figure,accelerating the bodies to the right.The magnitude of the force exerted by the connecting cord on body P is

A)zero.
B)less than F but not zero.
C)equal to F.
D)greater than F.

Question 13

If you swing a bucket of water fast enough in a vertical circle,at the highest point the water does not spill out.This happens because an outward force balances the pull of gravity on the water.

Question 14

If a satellite moves with constant speed in a perfectly circular orbit around the earth,what is the direction of the acceleration of the satellite?

A)in the forward direction
B)in the backward direction
C)outward away from the earth
D)inward toward the earth
E)The acceleration is zero because the speed is constant.

Question 15

In the figure,a 10-lb weight is suspended from two spring scales,each of which has negligible weight.Which one of the following statements about the readings in the scales is true?

A)Each scale will read 5 lb.
B)The top scale will read zero,the lower scale will read 10 lb.
C)The lower scale will read zero,the top scale will read 10 lb.
D)Each scale will show a reading between one and 10 lb,such that the sum of the two is 10 lb.However,exact readings cannot be determined without more information.
E)None of these is true.

Question 16

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice,causing the force of friction between the tires and the road to become zero.While the car is on the ice,it

A)moves along a straight-line path away from the center of the circle.
B)moves along a straight-line path toward the center of the circle.
C)moves along a straight-line path in its original direction.
D)continues to follow a circular path,but with a radius larger than the original radius.
E)moves along a path that is neither straight nor circular.

Question 17

Two boxes,A and B,are connected by a horizontal string S on a horizontal floor.A very light wire pulls horizontally on box B,as shown in the figure,with a force of 100 N.The reaction force to this pull is

A)the pull that box B exerts on string S.
B)the pull that string S exerts on box B.
C)the pull that string S exerts on box A.
D)the pull of box B on the wire.
E)the force that box A exerts on box B.

Question 18

A car goes around a circular curve on a horizontal road at constant speed.What is the direction of the friction force on the car due to the road?

A)tangent to the curve in the forward direction
B)tangent to the curve opposite to the direction of the car's motion
C)perpendicular to the curve outward
D)perpendicular to the curve inward
E)There is no friction on the car because its speed is constant.

Question 19

When a car goes around a circular curve on a horizontal road at constant speed,what force causes it to follow the circular path?

A)the normal force from the road
B)the friction force from the road
C)gravity
D)No force causes the car to do this because the car is traveling at constant speed and therefore has no acceleration.

Question 20

A push of magnitude P acts on a box of weight W as shown in the figure.The push is directed at an angle θ below the horizontal,and the box remains a rest.The box rests on a horizontal surface that has some friction with the box.The friction force on the box due to the floor is equal to

A)P sin θ.
B)P cos θ.
C)0.
D)P cos θ + W.
E)P + W.

Question 21

A race car traveling at a constant speed of 50 m/s drives around a circular track that is 500 m in diameter.What is the magnitude of the acceleration of the car?

A)0 m/s²
B)1.0 m/s²
C)10 m/s²
D)0.63 m/s²
E)2.2 m/s²

Question 22

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal.What must be true about force of static friction f on the block?

A)f > mg
B)f > mg cos θ
C)f > mg sin θ
D)f = mg cos θ
E)f = mg sin θ

Question 23

One way that future space stations may create artificial gravity is by rotating the station.Consider a cylindrical space station 380 m in diameter that is rotating about its longitudinal axis.Astronauts walk on the inside surface of the space station.How long will it take for each rotation of the cylinder if it is to provide "normal" gravity for the astronauts?

A)28 s
B)39 s
C)6.2 s
D)4.4 s

Question 24

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal.What is the magnitude of the force that the surface of the hill exerts on the sled?

A)200 N
B)120 N
C)160 N
D)150 N
E)0 N

Question 25

A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of the circular section of a dive.What is the radius of curvature of this section of the dive?

A)1.2 km
B)5.8 km
C)0.64 km
D)9.2 km
E)7.0 km

Question 26

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal.What must be true about normal force F on the block due to the ramp?

A)F > mg
B)F > mg cos θ
C)F > mg sin θ
D)F = mg cos θ
E)F = mg sin θ

Question 27

A point on a wheel of radius 40 cm that is rotating at a constant 5.0 revolutions per second is located 0.20 m from the axis of rotation.What is the acceleration of that point due to the spin of the wheel?

A)0.050 m/s²
B)1.4 m/s²
C)48 m/s²
D)200 m/s²
E)0.00 m/s²

Question 28

A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of a circular dive.What is the radius of curvature of the circular part of the path in which the plane is flying?

A)640 m
B)1200 m
C)7100 m
D)9200 m

Question 29

An object moves with a constant speed of 30 m/s on a circular track of radius 150 m.What is the acceleration of the object?

A)0 m/s²
B)0.17 m/s²
C)5.0 m/s²
D)6.0 m/s²

Question 30

The curved section of a horizontal highway is a circular unbanked arc of radius 740 m.If the coefficient of static friction between this roadway and typical tires is 0.40,what would be the maximum safe driving speed for this horizontal curved section of highway?

A)54 m/s
B)52 m/s
C)50 m/s
D)48 m/s
E)46 m/s

Question 31

A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km.What is the magnitude of the friction force required to keep the car from sliding?

A)9000 N
B)9800 N
C)300 N
D)900 N
E)3000 N

Question 32

Two boxes are connected to each other by a string as shown in the figure.The 10-N box slides without friction on the horizontal table surface.The pulley is ideal and the string has negligible mass.What is true about the tension T in the string?

A)T = 10 N
B)T = 20 N
C)T = 30 N
D)T < 30 N
E)T > 30 N

Question 33

Two objects have masses m and 5m,respectively.They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance.Which one of the following statements about these objects is correct?

A)It takes the lighter object 5 times longer to reach the bottom of the ramp than the heavier.
B)It takes the lighter object 10 times longer to reach the bottom of the ramp than the heavier.
C)It takes the heavier object 5 times longer to reach the bottom of the ramp than the lighter.
D)It takes the heavier object 10 times longer to reach the bottom of the ramp than the lighter.
E)The two objects reach the bottom of the ramp at exactly the same time.

Question 34

A 250-kg motorcycle goes around an unbanked turn of radius 13.7 m at a steady 96.5 km/h.What is the magnitude of the net force on the motorcycle?

A)719 N
B)2.95 × 10³ N
C)1.31 × 10⁴ N
D)4.31 × 10⁴ N

Question 35

Two objects of unequal masses,M and m (M > m),are connected by a very light cord passing over an ideal pulley of negligible mass.When released,the system accelerates,and friction is negligible.
Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

A)

B)

C)

D)

Question 36

You are driving at
On a freeway curve of radius
What is the magnitude of your acceleration?

A)36.0 m/s²
B)1.20 m/s²
C)20.8 m/s²
D)0.833 m/s²

Question 37

A particularly scary roller coaster contains a loop-the-loop in which the car and rider are completely upside down.If the radius of the loop is
With what minimum speed must the car traverse the loop so that the rider does not fall out while upside down at the top? Assume the rider is not strapped to the car.

A)11.4 m/s
B)12.5 m/s
C)10.1 m/s
D)14.9 m/s

Question 38

A 200-N sled of slides down a frictionless hillside that rises at 37° above the horizontal.What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?

A)200 N
B)120 N
C)160 N
D)150 N
E)0 N

Question 39

A 2.0-kg ball is moving with a constant speed of 5.0 m/s in a horizontal circle whose diameter is 1.0 m.What is the magnitude of the net force on the ball?

A)0 N
B)20 N
C)40 N
D)50 N
E)100 N

Question 40

A 0.50-kg toy is attached to the end of a 1.0-m very light string.The toy is whirled in a horizontal circular path on a frictionless tabletop.If the maximum tension that the string can withstand without breaking is 350 N.What is the maximum speed the mass can have without breaking the string?

A)700 m/s
B)26 m/s
C)19 m/s
D)13 m/s

Question 41

A future use of space stations may be to provide hospitals for severely burned persons.It is very painful for a badly burned person on Earth to lie in bed.In a space station,the effect of gravity can be reduced or even eliminated.How long should each rotation take for a doughnut-shaped hospital of 200-m radius so that persons on the outer perimeter would experience 1/10 the normal gravity of Earth?

A)91 min
B)8.7 min
C)4.6 min
D)1.5 min
E)0.011 min

Question 42

In a carnival ride,passengers stand with their backs against the wall of a cylinder.The cylinder is set into rotation and the floor is lowered away from the passengers,but they remain stuck against the wall of the cylinder.For a cylinder with a 2.0-m radius,what is the minimum speed that the passengers can have so they do not fall if the coefficient of static friction between the passengers and the wall is 0.25?

A)8.9 m/s
B)2.3 m/s
C)3.0 m/s
D)4.9 m/s
E)It depends on the mass of the passengers.

Question 43

Pulling out of a dive,the pilot of an airplane guides his plane into a vertical circle with a radius of 600 m.At the bottom of the dive,the speed of the airplane is 150 m/s.What is the apparent weight of the 70-kg pilot at that point?

A)3300 N
B)690 N
C)2600 N
D)490 N
E)1400 N

Question 44

A 50.0-kg crate is being pulled along a horizontal smooth surface.The pulling force is 10.0 N and is directed 20.0° above the horizontal.What is the magnitude of the acceleration of the crate?

A)0.0684 m/s²
B)0.188 m/s²
C)0.200 m/s²
D)0.376 m/s²
E)0.0728 m/s²

Question 45

A car moving at a steady 10 m/s on a level highway encounters a depression that has a circular cross-section with a radius of 30 m.The car maintains its speed as it drives through the depression.What is the normal force exerted by the seat of the car on a 60.0-kg passenger when the car is at the bottom of the depression?

A)200 N
B)390 N
C)790 N
D)490 N
E)590 N

Question 46

The curved section of a speedway is a circular arc having a radius of 190 m.This curve is properly banked for racecars moving at 34 m/s.At what angle with the horizontal is the curved part of the speedway banked?

A)32°
B)34°
C)30°
D)28°
E)26°

Question 47

A 1000-kg car is slowly picking up speed as it goes around a horizontal unbanked curve whose radius is 100 m.The coefficient of static friction between the tires and the road is 0.35.At what speed will the car begin to skid sideways?

A)9.3 m/s
B)24 m/s
C)34 m/s
D)35 m/s
E)19 m/s

Question 48

A highway curve of radius 100 m,banked at an angle of 45°,may be negotiated without friction at a speed of

A)22 m/s.
B)31 m/s.
C)44 m/s.
D)67 m/s.

Question 49

What is the proper banking angle for an Olympic bobsled to negotiate a 100-m radius turn at 35 m/s without skidding?

A)31°
B)41°
C)51°
D)61°

Question 50

A highway curve of radius 80 m is banked at 45°.Suppose that an ice storm hits,and the curve is effectively frictionless.What is the speed with which to take the curve without tending to slide either up or down the surface of the road?

A)9.4 m/s
B)28 m/s
C)780 m/s
D)The curve cannot be taken safely at any speed.

Question 51

A 20-g bead is attached to a light 120 cm-long string as shown in the figure.If the angle α is measured to be 18°,what is the speed of the mass?

A)0.55 m/s
B)2.0 m/s
C)3.8 m/s
D)1.3 m/s
E)1.1 m/s

Question 52

Pulling out of a dive,the pilot of an airplane guides his plane into a vertical circle.At the bottom of the dive,the speed of the airplane is 320 m/s.What is the smallest radius allowable for the vertical circle if the pilot's apparent weight is not to exceed 7.0 times his true weight?

A)1700 m
B)1500 m
C)2200 m
D)230 m
E)42 m

Question 53

A 1000-kg barge is being towed by means of two horizontal cables.One cable is pulling with a force of 80.0 N in a direction 30.0° west of north.In what direction should the second cable pull so that the barge will accelerate northward,if the force exerted by the cable is 120 N? Assume that the water exerts no appreciable frictional drag on the barge.

A)19.5° east of north
B)21.1° east of north
C)39.0° east of north
D)47.5° east of north
E)54.7° east of north

Question 54

A 20-g bead is attached to a light 120-cm-long string as shown in the figure.This bead moves in a horizontal circle with a constant speed of 1.5 m/s.What is the tension in the string if the angle α is measured to be 25°?

A)0.089 N
B)0.041 N
C)0.20 N
D)0.22 N
E)0.46 N

Question 55

A car moving at a steady 10 m/s on a level highway encounters a bump that has a circular cross-section with a radius of 30 m.The car maintains its speed over the bump.What is the normal force exerted by the seat of the car on a 60.0-kg passenger when the car is at the top of the bump?

A)200 N
B)390 N
C)790 N
D)490 N
E)590 N

Question 56

A car traveling at a steady 20 m/s rounds an 80-m radius horizontal unbanked curve with the tires on the verge of slipping.What is the maximum speed with which this car can round a second unbanked curve of radius 320 m if the coefficient of static friction between the car's tires and the road surface is the same in both cases?

A)160 m/s
B)80 m/s
C)70 m/s
D)40 m/s
E)30 m/s

Question 57

A 600-kg car is going around a banked curve with a radius of 110 m at a steady speed of 24.5 m/s.What is the appropriate banking angle so that the car stays on its path without the assistance of friction?

A)29.1°
B)13.5°
C)33.8°
D)56.2°
E)60.9°

Question 58

A 40-kg box is being pushed along a horizontal smooth surface.The pushing force is 15 N directed at an angle of 15° below the horizontal.What is the magnitude of the acceleration of the crate?

A)0.16 m/s²
B)0.36 m/s²
C)0.47 m/s²
D)0.39 m/s²
E)0.68 m/s²

Question 59

Two horizontal curves on a bobsled run are banked at the same angle,but one has twice the radius of the other.The safe speed (for which no friction is needed to stay on the run)for the smaller radius curve is v.What is the safe speed on the larger-radius curve?

A)v /
B)2v
C)v
D)v/2

Question 60

In order to simulate weightlessness for astronauts in training,they are flown in a vertical circle.If the passengers are to experience weightlessness,how fast should an airplane be moving at the top of a vertical circle with a radius of 2.5 km?

A)79 m/s
B)310 m/s
C)260 m/s
D)160 m/s
E)510 m/s

Question 61

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a rope that goes over an ideal pulley.If the masses are gently released from rest,how long does it take for the 3.0-kg mass to rise by 1.0 m?

A)0.41 s
B)0.74 s
C)0.82 s
D)1.8 s
E)0.90 s

Question 62

An object slides on a level floor.It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s².What is the coefficient of kinetic friction between the object and the floor?

A)0.24
B)0.48
C)0.12
D)It is impossible to determine without knowing the mass of the object.

Question 63

The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30,respectively.What is the force of friction on the box when a 15-N horizontal push is applied to the box?

A)12 N
B)8.8 N
C)15 N
D)6.0 N
E)4.5 N

Question 64

A tightrope walker walks across a 30-m long wire tied between two poles.The center of the wire is displaced vertically downward by 1.0 m when he is halfway across.If the tension in both halves of the wire at this point is
What is the mass of the tightrope walker? Neglect the mass of the wire.

A)85 kg
B)43 kg
C)74 kg
D)91 kg

Question 65

The figure shows a 100-kg block being released from rest from a height of 1.0 m.It then takes 0.53 s for it to reach the floor.What is the mass m of the block on the left? There is no friction or mass in the pulley,and the connecting rope is very light.

A)16 kg
B)14 kg
C)13 kg
D)11 kg

Question 66

In the figure,block A has a mass of 3.00 kg.It rests on a smooth horizontal table and is connected by a very light horizontal string over an ideal pulley to block B,which has a mass of 2.00 kg.When block B is gently released from rest,how long does it take block B to travel 80.0 cm?

A)0.404 s
B)0.494 s
C)0.639 s
D)0.785 s
E)0.935 s

Question 67

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley.If the masses are gently released,what is the resulting acceleration of the masses?

A)0.00 m/s²
B)3.7 m/s²
C)2.5 m/s²
D)4.9 m/s²
E)6.1 m/s²

Question 68

A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction.What is the tension in each cable?

A)231 N
B)400 N
C)800 N
D)2560 N
E)3920 N

Question 69

A 10-kg sign is held by two ropes as shown in the figure.What is the tension on rope A?

A)44 N
B)69 N
C)72 N
D)88 N
E)98 N

Question 70

Two forces act on a
Object.One force has magnitude 65 N directed 59° clockwise from the positive x-axis,and the other has a magnitude 35 N at 32° clockwise from the positive y-axis.What is the magnitude of this object's acceleration?

A)1.1 m/s²
B)1.3 m/s²
C)1.5 m/s²
D)1.7 m/s²

Question 71

An object is being acted upon by three forces and as a result moves with a constant velocity.One force is 60.0 N along the +x-axis,and the second is 75.0 N along the +y-axis.What is the magnitude of the third force?

A)135 N
B)15.0 N
C)48.0 N
D)67.5 N
E)96.0 N

Question 72

As shown in the figure,a 10-kg block on a perfectly smooth horizontal table is connected by a horizontal string to a 63-kg block that is hanging over the edge of the table.What is the magnitude of the acceleration of the 10-kg block when the other block is gently released?

A)8.5 m/s²
B)8.1 m/s²
C)7.5 m/s²
D)9.0 m/s²

Question 73

Three boxes rest side-by-side on a smooth,horizontal floor.Their masses are 5.0 kg,3.0 kg,and 2.0 kg,with the 3.0-kg mass in the center.A force of 50 N pushes on the 5.0-kg box,which pushes against the other two boxes.What magnitude force does the 5.0-kg box exert on the 3.0-kg box?

A)0 N
B)10 N
C)25 N
D)40 N
E)50 N

Question 74

A 10.0-kg picture is held in place by two wires,the first one hanging at 50.0° to the left of the vertical and the second one at 45.0° to the right of the vertical.What is the tension in the first wire?

A)69.6 N
B)50.8 N
C)98.1 N
D)69.4 N
E)23.8 N

Question 75

A piano mover raises a 1000-N piano at a constant speed using a very light rope in a frictionless pulley system,as shown in the figure.With what force is the mover pulling down on the rope?

A)2000 N
B)1000 N
C)500 N
D)250 N
E)Depends on the speed of the piano.

Question 76

A load is being lifted vertically upwards by means of two cables attached to it.The first cable exerts a force of 600 N at an angle of 35.0° to the left of the vertical.The second cable exerts a force of 1300 N.At what angle to the right of the vertical is the second cable pulling?

A)15.4°
B)16.2°
C)30.8°
D)67.8°
E)75.8°

Question 77

A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth,level floor.A horizontal force of 32 N is applied to the 5.0-kg box pushing it against the 3.0-kg box,and,as a result,both boxes slide along the floor.How hard do the two boxes push against each other?

A)12 N
B)20 N
C)24 N
D)32 N
E)0 N

Question 78

The figure shows a block of mass M hanging at rest.The light wire fastened to the wall is horizontal and has a tension of 38 N.The wire fastened to the ceiling is also very light,has a tension of
And makes an angle θ with the ceiling.Find the angle θ.

A)50°
B)40°
C)33°
D)65°
E)45°

Question 79

A 3.0-kg and a 5.0-kg box rest side-by-side on a perfectly smooth,level floor.A horizontal force of 32 N is applied to the 3.0-kg box pushing it against the 5.0-kg box,and,as a result,both boxes slide along the floor.How hard do the two boxes push against each other?

A)12 N
B)20 N
C)24 N
D)32 N
E)0 N

Question 80

A 6.00-kg ornament is held at rest by two light wires that form 30° angles with the vertical,as shown in the figure.An external force of magnitude F acts vertically downward on the ornament.The tension exerted by each of the two wires is denoted by T.A free-body diagram,showing the four forces that act on the box,is shown in the figure.If the magnitude of force F is 410 N,what is the magnitude of the tension T?

A)271 N
B)235 N
C)188 N
D)376 N
E)470 N