Deck 5: Applying Newtons Laws

Question 1

Two objects have masses m and 5m,respectively.They both are placed side by side on a frictionless inclined plane and allowed to slide down from rest.

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

Answer 1

The two objects reach the bottom of the incline at the same time.

Question 2

A 60.0-kg person rides in elevator while standing on a scale.The elevator is traveling downward but slowing down at a rate of 2.00 m/s².The reading on the scale is closest to

A) 589 N.
B) 708 N.
C) 469 N.
D) 120 N.
E) 349 N.

Answer 2

708 N.

Question 3

Two objects having masses m₁ and m₂ are connected to each other as shown in the figure and are released from rest.There is no friction on the table surface or in the pulley.The masses of the pulley and the string connecting the objects are completely negligible.What must be true about the tension T in the string just after the objects are released?

A) T = m₂g
B) T > m₂g
C) T < m₂g
D) T = m₁g
E) T > m₁g

Answer 3

T < m₂g

Question 4

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

Question 5

Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P.The tension in the wire is T (see figure).Which one of the following relationships between T and P must be true?

A) T > P
B) T = P
C) P + T = 125 N
D) P = T + 25 N
E) P = T + 100 N

Question 6

Suppose the force of the air drag on an object is proportional to the speed of the object and in the direction opposite the object's velocity.If you throw an object upward,the magnitude of its acceleration is greatest

A) right after the object is released.
B) at the top of its trajectory.
C) The acceleration of the object is the same throughout the entire trajectory.

Question 7

Two bodies P and Q on a smooth horizontal surface are connected by a light cord.The mass of P is greater than that of Q.A horizontal force (of magnitude F) is applied to 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 will be

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

Question 8

A brick is resting on a rough incline as shown in the figure.The friction force acting on the brick,along the incline,is

A) zero.
B) equal to the weight of the brick.
C) greater than the weight of the brick.
D) less than the weight of the brick.

Question 9

A 615 N student standing on a scale in an elevator notices that the scale reads .From this information,the student knows that the elevator must be moving

A) downward.
B) upward.
C) You cannot tell if it is moving upward or downward.

Question 10

Which one of the following free-body diagrams best represents the free-body diagram,with correct relative force magnitudes,of a person in an elevator that is traveling upward but is gradually slowing down at a rate of ? _f is the force of the floor on the person and _g is the force of gravity on the person.

A)
B)
C)
D)
E)

Question 11

A string is attached to the rear-view mirror of a car.A ball is hanging at the other end of the string.The car is driving around in a circle,at a constant speed.Which of the following lists gives all of the forces directly acting on the ball?

A) tension and gravity
B) tension
C) tension, gravity, and the centripetal force
D) tension, gravity, the centripetal force, and friction

Question 12

Two objects are connected by a very light flexible string as shown in the figure,where and .You can ignore friction and the mass of the pulley. (a)Draw free-body diagrams for each object.
(b)Calculate the magnitude of the acceleration of each object.
(c)Calculate the tension in the string.

Question 13

Suppose a highway curve is properly banked to eliminate friction for a speed of 45 mph.If your tires were bald and you wanted to avoid sliding on the road,you would have to drive

A) somewhat below 45 mph.
B) somewhat above 45 mph.
C) at exactly 45 mph.

Question 14

When a parachutist jumps from an airplane,he eventually reaches a constant speed,called the terminal speed.Once he has reached terminal speed

A) his acceleration is equal to g.
B) the force of air drag on him is equal to zero.
C) the force of air drag on him is equal to g.
D) his speed is equal to g.
E) the force of air drag on him is equal to his weight.

Question 15

Which one of the following free-body diagrams best represents the free-body diagram,with correct relative force magnitudes,of a person in an elevator that is traveling upward with an unchanging velocity? _f is the force of the floor on the person and _g is the force of gravity on the person.

A)
B)
C)
D)
E)

Question 16

A box slides down a frictionless plane inclined at an angle θ above the horizontal.The gravitational force on the box is directed

A) parallel to the plane in the same direction as the movement of the box.
B) parallel to the plane in the opposite direction as the movement of the box.
C) perpendicular to the plane.
D) vertically.
E) at an angle θ below the inclined plane.

Question 17

A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s.The vector sum of all the forces acting on this crate must point down the ramp.

Question 18

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

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

Question 19

A 60.0-kg person rides in an elevator while standing on a scale.The scale reads .The acceleration of the elevator is closest to

A) 3.13 m/s² downward.
B) 6.67 m/s² downward.
C) zero.
D) 9.80 m/s² downward.
E) 6.67 m/s² upward.

Question 20

Two unequal masses M and m (M > m)are connected by a light cord passing over a pulley of negligible mass,as shown in the figure.When released,the system accelerates.Friction is negligible.Which figure below gives the correct free-body force diagrams for the two masses in the moving system?

A)
B)
C)
D)

Question 21

A 20.0-N box rests on a 50.0-N box on a perfectly smooth horizontal floor.When a horizontal pull to the right is exerted on the lower box (see figure),both boxes move together.Find the magnitude and direction of the net external force on the upper box.

Question 22

A system comprising blocks,a light frictionless pulley,a frictionless incline,and connecting ropes is shown in the figure.The 9.0-kg block accelerates downward when the system is released from rest.The tension in the rope connecting the block and the block is closest to

A) 30 N.
B) 33 N.
C) 36 N.
D) 39 N.
E) 42 N.

Question 23

A block is given a very brief push up a 20.0° frictionless incline to give it an initial speed of 12.0 m/s.
(a)How far along the surface of the plane does the block slide before coming to rest?
(b)How much time does it take to return to its starting position?

Question 24

A 4.00-kg block rests between the floor and a 3.00-kg block as shown in the figure.The 3.00-kg block is tied to a wall by a horizontal rope.If the coefficient of static friction is 0.800 between each pair of surfaces in contact,what horizontal force F must be applied to the block to make it move?

A) 16.2 N
B) 54.9 N
C) 21.1 N
D) 23.5 N
E) 78.4 N

Question 25

A wooden block A of mass 4.0 kg slides on a frictionless table when pulled using a massless string and pulley array by a hanging box B of mass 5.0 kg,as shown in the figure.What is the acceleration of block A as it slides on the frictionless table? Hint: Think carefully about the acceleration constraint.

A) 4.1 m/s²
B) 3.5 m/s²
C) 3.1 m/s²
D) 2.7 m/s²

Question 26

Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure.The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N.What is the mass M?

A) 8.33 kg
B) 33.9 kg
C) 35.0 kg
D) 52.8 kg
E) 95.0 kg

Question 27

A driver in a car traveling at slams on the brakes and skids to a stop.If the coefficient of friction between the tires and the horizontal road is 0.80,how long will the skid marks be?

A) 26 m
B) 21 m
C) 33 m
D) 24 m

Question 28

Jason takes off from rest across level water on his jet-powered skis.The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible).The skis have a thrust of and a coefficient of kinetic friction on water of 0.10.Unfortunately,the skis run out of fuel after only 67 s.How far has Jason traveled when he finally coasts to a stop?

A) 10,000 m
B) 7600 m
C) 5400 m
D) 3800 m

Question 29

A 6.00-kg block is in contact with a 4.00-kg block on a horizontal frictionless surface as shown in the figure.The 6.00-kg block is being pushed by a horizontal force as shown.What is the magnitude of the force that the block exerts on the block?

A) 6.00 N
B) 20.0 N
C) 8.00 N
D) 4.00 N
E) 10.0 N

Question 30

Kieran takes off from rest down a 50 m high,10° slope on his jet-powered skis.The skis have a thrust of 280 N parallel to the surface of the slope.The combined mass of skis and Kieran is 50 kg (the fuel mass is negligible).Kieran's speed at the bottom is 40 m/s.What is the coefficient of kinetic friction of his skis on snow?

A) 0.47
B) 0.58
C) 0.23
D) 0.29

Question 31

Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure.The tension in the wire connecting the and objects is measured to be .What is the tension in wire A?

A) 87.5 N
B) 245 N
C) 280 N
D) 333 N
E) 517 N

Question 32

Three boxes in contact 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 box in the center.A force of 50 N pushes on the 5.0-kg box,which pushes against the other two boxes.
(a)Draw the free-body diagrams for each of the boxes.
(b)What magnitude force does the 3.0-kg box exert on the 5.0-kg box?
(c)What magnitude force does the 3.0-kg box exert on the 2.0-kg box?

Question 33

In a shuffleboard game,the puck slides a total of before coming to rest.If the coefficient of kinetic friction between the puck and the horizontal board is 0.28,what was the initial speed of the puck?

A) 8.1 m/s
B) 29.0 m/s
C) 6.5 m/s
D) 7.3 m/s

Question 34

A 50.0-kg box rests on a horizontal surface.The coefficient of static friction between the box and the surface is 0.300 and the coefficient of kinetic friction is 0.200.What is the friction force on the box if
(a)a horizontal 140-N push is applied to it?
(b)a horizontal 175-N push is applied to it?

Question 35

A factory robot drops a 10 kg computer onto a conveyor belt running at 3.1 m/s.The materials are such that μ_s = 0.50 and μ_k = 0.30 between the belt and the computer.How far is the computer dragged before it is riding smoothly on the belt?

A) 1.6 m
B) 0.98 m
C) 2.3 m
D) 3.0 m

Question 36

Jason takes off from rest across level water on his jet-powered skis.The combined mass of Jason and his skis is (the mass of the fuel is negligible).The skis have a thrust of and a coefficient of kinetic friction on water of 0.10.Unfortunately,the skis run out of fuel after only .What is Jason's top speed?

A) 81 m/s
B) 130 m/s
C) 13 m/s
D) 48 m/s

Question 37

The figure shows two 1.0 kg-blocks connected by a rope.A second rope hangs beneath the lower block.Both ropes have a mass of 250 g.The entire assembly is accelerated upward at 2.3 m/s² by force .What is the tension at the top end of rope 1?

A) 18 N
B) 15 N
C) 2.9 N
D) 3.5 N

Question 38

A 150-N box is being pulled horizontally in a wagon accelerating uniformly at .The box does not move relative to the wagon,the coefficient of static friction between the box and the wagon's surface is 0.600,and the coefficient of kinetic friction is 0.400.The friction force on this box is closest to

A) 450 N.
B) 90.0 N.
C) 60.0 N.
D) 45.9 N.

Question 39

A child on a sled starts from rest at the top of a 15° slope.If the trip to the bottom takes how long is the slope? Assume that frictional forces may be neglected.

A) 293 m
B) 586 m
C) 1130 m
D) 147 m

Question 40

The figure shows a 100-kg block being released from rest from a height of 1.0 m.It then takes it 0.90 s to reach the floor.What is the mass m of the other block? The pulley has no appreciable mass or friction.

A) 60 kg
B) 54 kg
C) 48 kg
D) 42 kg

Question 41

A person is dragging a packing crate of mass 100 kg across a rough horizontal floor where the coefficient of kinetic friction is 0.400.He exerts a force F sufficient to accelerate the crate forward.At what angle above horizontal should his pulling force be directed in order to achieve the maximum acceleration?

A) 21.8°
B) 27.7°
C) 30°
D) 34.5°
E) 45°

Question 42

Two blocks are connected by a string that goes over an ideal pulley as shown in the figure.Block A has a mass of 3.00 kg and can slide over a rough plane inclined 30.0° to the horizontal.The coefficient of kinetic friction between block A and the plane is 0.400.Block B has a mass of 2.77 kg.What is the acceleration of the blocks?

A) 0.392 m/s²
B) 1.96 m/s²
C) 3.12 m/s²
D) 5.35 m/s²
E) 0.00 m/s²

Question 43

The figure shows two packages that start sliding down a 20° ramp from rest a distance along the ramp from the bottom.Package A has a mass of 5.0 kg and a coefficient of kinetic friction 0.20 between it and the ramp.Package B has a mass of 10 kg and a coefficient of kinetic friction 0.15 between it and the ramp.How long does it take package A to reach the bottom?

A) 2.7 s
B) 3.0 s
C) 3.2 s
D) 3.5 s

Question 44

A 6.0 kg box slides down an inclined plane that makes an angle of 39° with the horizontal.If the coefficient of kinetic friction is 0.19,at what rate does the box accelerate down the slope?

A) 4.7 m/s²
B) 5.2 m/s²
C) 5.5 m/s²
D) 6.2 m/s²

Question 45

Three objects are connected as shown in the figure.The strings and frictionless pulleys have negligible masses,and the coefficient of kinetic friction between the 2.0-kg block and the table is 0.25.What is the acceleration of the 2.0-kg block?

A) 2.5 m/
B) 1.7 m/
C) 3.2 m/
D) 4.0 m/

Question 46

In the figure,two wooden blocks each of 0.30 kg mass are connected by a string that passes over a very light frictionless pulley.One block slides on a horizontal table,while the other hangs suspended by the string,as shown in the figure.At time t = 0,the suspended block is 0.80 m over the floor,and the blocks are released from rest.After 2.5 s,the suspended block reaches the floor.What is the coefficient of kinetic friction between the table and the sliding block?

A) 0.35
B) 0.52
C) 0.84
D) 0.65
E) 0.95

Question 47

A 200 g hockey puck is launched up a metal ramp that is inclined at a 30° angle.The coefficients of static and kinetic friction between the hockey puck and the metal ramp are and ,respectively.The puck's initial speed is .What vertical height does the puck reach above its starting point?

A) 130 m
B) 270 m
C) 200 m
D) 66 m

Question 48

A box is sliding down an incline tilted at a 12.0° angle above horizontal.The box is initially sliding down the incline at a speed of 1.50 m/s.The coefficient of kinetic friction between the box and the incline is 0.340.How far does the box slide down the incline before coming to rest?

A) 0.920 m
B) 2.33 m
C) 1.78 m
D) 0.720 m
E) The box does not stop. It accelerates down the plane.

Question 49

Two boxes are connected by a weightless cord running over a very light frictionless pulley as shown in the figure.Box A,of mass 8.0 kg,is initially at rest on the top of the table.The coefficient of kinetic friction between box A and the table is 0.10.Box B has a mass of 15.0 kg,and the system begins to move just after it is released. (a)Draw the free-body diagrams for each of the boxes,identifying all of the forces acting on each one.
(b)Calculate the acceleration of each box.
(c)What is the tension in the cord?

Question 50

A pickup truck is moving at 25 m/s with a toolbox of mass m resting on the bed of the truck 2.5 m behind the cab.Suddenly the brakes are applied,causing the toolbox to slide,and the truck comes to a stop in 4.7 s.The coefficient of kinetic friction between the toolbox and the bed of the truck is 0.28.After the brakes are applied,how much time elapses before the toolbox strikes the cab?

Question 51

A 4.00-kg box sits atop a 10.0-kg box on a horizontal table.The coefficient of kinetic friction between the two boxes and between the lower box and the table is 0.600,while the coefficient of static friction between these same surfaces is 0.800.A horizontal pull to the right is exerted on the lower box,as shown in the figure,and the boxes move together.What is the friction force on the UPPER box?

A) 19.3 N to the right
B) 19.3 N to the left
C) 23.5 N to the right
D) 31.4 N to the right
E) 31.4 N to the left

Question 52

A packing crate rests on a horizontal surface.It is acted on by three horizontal forces: 600 N to the left,200 N to the right,and friction.The weight of the crate is 400 N.If the 600-N force is removed,the resultant force acting on the crate is

A) zero.
B) 200 N to the right.
C) 200 N to the left.
D) 400 N to the left.
E) impossible to determine from the information given.

Question 53

You push downward on a box at an angle 25° below the horizontal with a force of .If the box is on a flat horizontal surface for which the coefficient of static friction with the box is 0.76,what is the mass of the heaviest box you will be able to move?

A) 59 kg
B) 68 kg
C) 54 kg
D) 82 kg

Question 54

A 200 g hockey puck is launched up a metal ramp that is inclined at a 30° angle.The coefficients of static and kinetic friction between the hockey puck and the metal ramp are and ,respectively.The puck's initial speed is 4.9 m/s.What speed does it have when it slides back down to its starting point?

A) 2.8 m/s
B) 3.5 m/s
C) 4.2 m/s
D) 4.9 m/s

Question 55

A 4.00-kg block rests on a 30.0° incline as shown in the figure.If the coefficient of static friction between the block and the incline is 0.700,what magnitude horizontal force F must act on the block to start it moving up the incline?

A) 34.0 N
B) 51.1 N
C) 54.7 N
D) 84.0 N
E) 76.4 N

Question 56

In the figure,a T-bar ski tow pulls a skier up a hill inclined at 10° above horizontal.The skier starts from rest and is pulled by a cable that exerts a tension T at an angle of 30° above the surface of the hill.The mass of the skier is 60 kg and the effective coefficient of kinetic friction between the skis and the snow is 0.100.What is the maximum tension in the cable if the starting acceleration is not to exceed 0.400 g?

A) 246 N
B) 366 N
C) 431 N
D) 187 N
E) 535 N

Question 57

A system comprised blocks,a light frictionless pulley,and connecting ropes is shown in the figure.The 9.0-kg block is on a perfectly smooth horizontal table.The surfaces of the 12-kg block are rough,with between the block and the table.If the 5.0-kg block accelerates downward when it is released,find its acceleration.

A) 1.0 m/s²
B) 1.2 m/s²
C) 1.4 m/s²
D) 1.6 m/s²
E) 1.8 m/s²

Question 58

A 50.0-kg block is being pulled up a 16.0° slope by a force of 250 N which is parallel to the slope.The coefficient of kinetic friction between the block and the slope is 0.200.What is the magnitude of the acceleration of the block?

A) 0.528 m/
B) 0.158 m/
C) 0.412 m/
D) 0.983 m/
E) 0.260 m/

Question 59

A rope pulls on the lower block in the figure with a tension force of 20 N.The coefficient of kinetic friction between the lower block and the surface is 0.16.The coefficient of kinetic friction between the lower block and the upper block is also 0.16.The pulley has no appreciable mass or friction.What is the acceleration of the 2.0 kg block?

A) 4.1 m/s²
B) 5.1 m/s²
C) 8.4 m/s²
D) 9.2 m/s²

Question 60

Block A of mass 5.0 kg and block X are attached to a rope which passes over a pulley,as shown in the figure.An 80-N force P is applied horizontally to block A,keeping it in contact with a rough vertical face.The coefficients of static and kinetic friction between the wall and block A are μ_s = 0.40 and μ_k = 0.30.The pulley is light and frictionless.The mass of block X is adjusted until block A moves upward with an acceleration of 1.6 m/s².What is the mass of block X?

A) 9.9 kg
B) 9.3 kg
C) 8.7 kg
D) 8.1 kg
E) 7.5 kg

Question 61

A system of blocks and a frictionless pulley is shown in the figure.Block A has a mass of 2.0 kg and is on a rough horizontal surface for which μ_s = 0.40 between the surface and block A.The rope pulls horizontally on block A.Block C has a mass of 1.0 kg.An external force ,applied vertically to block A,maintains the system at rest as shown in the figure.What is the friction force on block A?

A) 6.3 N
B) 6.9 N
C) 7.5 N
D) 5.7 N
E) 5.1 N

Question 62

A 1520-N crate is to be held in place on a ramp that rises at 30.0° above the horizontal (see figure).The massless rope attached to the crate makes a 22.0° angle above the surface of the ramp.The coefficients of friction between the crate and the surface of the ramp are and .The pulley has no appreciable mass or friction.What is the MAXIMUM weight w that can be used to hold this crate stationary on the ramp?

Question 63

A car enters a 300-m radius horizontal curve on a rainy day when the coefficient of static friction between its tires and the road is 0.600.What is the maximum speed at which the car can travel around this curve without sliding?

A) 29.6 m/s
B) 33.1 m/s
C) 24.8 m/s
D) 42.0 m/s
E) 37.9 m/s

Question 64

The figure shows a 2000 kg cable car descending a high hill.A counterweight of mass on the other side of the hill aids the brakes in controlling the cable car's speed.The rolling friction of both the cable car and the counterweight are negligible.How much braking force does the cable car need to descend at constant speed?

A) 3800 N
B) 2900 N
C) 2000 N
D) 980 N

Question 65

Engineers are designing a curved section of a highway.If the radius of curvature of the curve is at what angle should the curve be banked so that a car traveling at 29.0 m/s will stay on the road without the aid of frictional forces?

A) 23.9°
B) 16.7°
C) 21.0°
D) 26.1°

Question 66

Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P.The tension in the wire is T (see figure).P is closest to

A) 25 N.
B) 125 N.
C) 187.5 N.
D) 245 N.
E) 1225 N.

Question 67

Block A of mass 8.0 kg and block X are attached to a rope that passes over a pulley.A 50-N force P is applied horizontally to block A,keeping it in contact with a rough vertical face.The coefficients of static and kinetic friction between the wall and block A are and .The pulley is light and frictionless.In the figure,the mass of block X is adjusted until block A descends at constant velocity of 4.75 cm/s when it is set into motion.What is the mass of block X?

A) 6.5 kg
B) 7.2 kg
C) 8.0 kg
D) 8.8 kg
E) 9.5 kg

Question 68

In the figure,a block of mass M hangs at rest.The rope that is fastened to the wall is horizontal and has a tension off 52 N.The rope that is fastened to the ceiling has a tension of and makes an angle θ with the ceiling.What is the angle θ?

A) 55°
B) 35°
C) 30°
D) 63°
E) 45°

Question 69

A 600-kg car traveling at is going around a curve having a radius of 120 m that is banked at an angle of 20°.
(a)Is the curve properly banked for the car's speed?
(b)What is the minimum coefficient of static friction required between the road and the car's tires so the car does not skid?

Question 70

A 23 kg mass is connected to a nail on a frictionless table by a massless string 1.3 m long.There is no appreciable friction between the nail and the string.If the tension in the string is while the mass moves in a uniform circle on the table,how long does it take for the mass to make one complete revolution?

A) 4.8 s
B) 3.8 s
C) 4.5 s
D) 5.2 s

Question 71

The figure shows two forces,each of magnitude 4.6 N,acting on an object.The angle between these forces is 40°,and they make equal angles above and below the horizontal.What third force will cause the object to be in equilibrium (acceleration equals zero)?

A) 8.6 N pointing to the right
B) 7.0 N pointing to the right
C) 4.3 N pointing to the right
D) 3.5 N pointing to the right

Question 72

Two blocks are connected by a string that goes over an ideal pulley as shown in the figure and pulls on block A parallel to the surface of the plane.Block A has a mass of 3.00 kg and can slide along a rough plane inclined 30.0° to the horizontal.The coefficient of static friction between block A and the plane is 0.400.What mass should block B have in order to start block A sliding up the plane?

Question 73

A car travels at a steady 40.0 m/s around a horizontal curve of radius 200 m.What is the minimum coefficient of static friction between the road and the car's tires that will allow the car to travel at this speed without sliding?

A) 1.23
B) 0.816
C) 0.736
D) 0.952
E) 0.662

Question 74

A 600-kg car is going around a banked curve with a radius of 110 m at a speed of .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 75

A traffic light weighing 100 N is supported by two ropes as shown in the figure.The tensions in the ropes are closest to

A) 50 N.
B) 56 N.
C) 63 N.
D) 66 N.
E) 83 N.

Question 76

A 600-kg car traveling at is going around a curve having a radius of 120 m that is banked at an angle of 25.0°.The coefficient of static friction between the car's tires and the road is 0.300.What is the magnitude of the force exerted by friction on the car?

A) 1590 N
B) 3430 N
C) 7240 N
D) 7820 N
E) 795 N

Question 77

A 250-kg crate is on a rough ramp,inclined at 30° above the horizontal.The coefficient of kinetic friction between the crate and ramp is 0.22.A horizontal force of 5000 N is applied to the crate,pushing it up the ramp.What is the acceleration of the crate?

A) 8.4 m/s²
B) 10 m/s²
C) 12 m/s²
D) 13 m/s²
E) 3.4 m/s²

Question 78

The figure shows two forces acting at right angles on an object.They have magnitudes and .What third force will cause the object to be in equilibrium (acceleration equals zero)?

A) 6.6 N at 162° counterclockwise from ₁
B) 6.6 N at 108° counterclockwise from ₁
C) 4.2 N at 162° counterclockwise from ₁
D) 4.2 N at 108° counterclockwise from ₁

Question 79

A car drives over a hilltop that has a radius of curvature 0.120 km at the top of the hill.At what speed would the car be traveling when it tires just barely lose contact with the road when the car is at the top of the hill?

A) 45.5 m/s
B) 41.8 m/s
C) 34.3 m/s
D) 22.2 m/s
E) 27.6 m/s

Question 80

A 1000-kg car is slowly picking up speed as it goes around a horizontal curve whose radius is 100 m.The coefficient of static friction between the tires and the road is 0.350.At what speed will the car begin to skid sideways?

A) 9.25 m/s
B) 23.6 m/s
C) 34.3 m/s
D) 35.0 m/s
E) 18.5 m/s