Deck 5: Applying Newtons Laws

Question 1

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

Answer 1

D

Question 2

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle ? 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 ?
B)P cos ?
C)0
D)P cos ? + W
E)P + W

Answer 2

P cos ?

Question 3

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

Answer 3

D

Question 4

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 $\overrightarrow { \mathbf { F } }$ 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 5

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 6

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 7

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 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

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 10

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 11

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 12

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 13

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 14

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 15

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 16

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 17

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle ? 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 ?.
D)W + P sin ?.
E)W - P sin ?.

Question 18

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 19

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 20

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 21

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 22

Two forces act on a $55 - \mathrm { kg }$ 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 23

A very light wire is used to hang a series of 8.0-kg bricks. This wire will break if the tension in it exceeds 450 N. The bricks are hung one below the other from a hook in the ceiling using this wire, as shown in the figure.
(a)How many whole bricks can be hung without breaking the wire?
(b)If you add one more brick to the number found in part (a), which string will break?

Question 24

Three objects are connected by weightless flexible strings as shown in the figure. The pulley has no appreciable mass or friction, and the string connected to the block on the horizontal bench pulls on it parallel to the bench surface. The coefficients of friction between the bench and the block on it are µ_s = 0.66 and µ_k = 0.325. You observe that this system remains at rest.
(a)Find the mass of the hanging object A.
(b)What is the magnitude of the friction force on the block on the bench?

Question 25

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 26

A 30.0-kg load is being held in place using massless wires in the ideal pulley arrangement shown in the figure. What is the magnitude of the force F?

Question 27

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 28

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 29

An object is being acted upon by three forces and moves with a constant velocity. One force is 60 N along the +x-axis, the second is 75 N along a direction making a counterclockwise angle of 150° with the +x-axis.
(a)What is the magnitude of the third force?
(b)What is the direction of the third force, measured clockwise from the +x-axis?

Question 30

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 $$59 \mathrm {~N} ,$$ and makes an angle ? with the ceiling. Find the angle ?.

A)50°
B)40°
C)33°
D)65°
E)45°

Question 31

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 32

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 33

A 5.0-kg block and a 4.0-kg block are connected by a 0.6 kg rod, as shown in the figure. The links between the blocks and the rod are denoted by A and B. A vertical upward force of magnitude F is applied to the upper block. The blocks and rod assembly are moving downward at constant velocity of 85 cm/s.
(a)What is the magnitude of the applied force F?
(b)What magnitude force does link A exert?

Question 34

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 35

As shown in the figure, two blocks are connected by a very light string, and the upper block is pulled upward by a different string. The masses of the upper and lower blocks are 300 g and 240 g, respectively. The string between the blocks will break if its tension exceeds 3.6 N, and the string that pulls the combination upward will break if its tension exceeds 7.8 N.
(a)What is the largest upward acceleration that the blocks can be given without either string breaking?
(b)If the upward acceleration is slightly higher than this, which string breaks, the upper one or the lower one?

Question 36

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 37

A locomotive is pulling 9 freight cars, each of which is loaded with the same weight. The mass of each loaded car is $37,000 \mathrm {~kg} ,$ and we can neglect friction on these 9 cars. If the train is accelerating forward at $0.81 \mathrm {~m} / \mathrm { s } ^ { 2 }$ on a level track, what is the tension in the coupling between the second and third cars? (The car nearest the locomotive is counted as the first car.)

Question 38

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 39

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 $6294 \mathrm {~N}$ 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 40

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

Question 41

In a shuffleboard game, the puck slides a total of 12 m on a horizontal surface before coming to rest. If the coefficient of kinetic friction between the puck and board is 0.10, what was the initial speed of the puck?

A)4.8 m/s
B)48.5 m/s
C)3.8 m/s
D)4.3 m/s

Question 42

During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the horizontal ice before it stops due to friction. What is the coefficient of kinetic friction between the puck and the ice?

A)0.090
B)0.10
C)0.11
D)0.12

Question 43

A 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the surface is 0.40, and the coefficient of kinetic friction is 0.30. What is the force of friction on the box?

A)32 N
B)200 N
C)220 N
D)250 N
E)620 N

Question 44

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 45

A locomotive is pulling three train cars along a level track with a force of 100,000 N. The car next to the locomotive has a mass of 80,000 kg, the next one, 50,000 kg, and the last one, 70,000 kg. You can neglect the friction on the cars being pulled.
(a)What is the magnitude of the force between that the 80,000-kg car exerts on the 50,000-kg car?
(b)What is the magnitude of the force that the 50,000-kg car exerts on the 70,000-kg car?

Question 46

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30, and the coefficient of kinetic friction is 0.20. What horizontal force must be applied to the box to cause it to start sliding along the surface?

Question 47

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 48

A horizontal 52-N force is needed to slide a $50 - \mathrm { kg }$ box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor?

A)0.11
B)0.09
C)0.10
D)0.13

Question 49

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 50

Three blocks, light connecting ropes, and a light frictionless pulley comprise a system, as shown in the figure. An external force of magnitude P is applied downward on block A, causing block A to accelerate downward at a constant 2.5 m/s². The tension in the rope connecting block B and block C is equal to 60 N.
(a)What is the magnitude of the force P?
(b)What is the mass of block C?

Question 51

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 52

A 5.0-kg block and a 4.0-kg block are connected by a 0.6 kg rod, as shown in the figure. The links between the blocks and the rod are denoted by A and B. A vertical upward force of magnitude F of magnitude 150 N is applied to the upper block. What magnitude force does each of the links A and B exert?

Question 53

A bulldozer attempts to drag a log weighing 500 N along the rough horizontal ground. The cable attached to the log makes an angle of 30° above the ground. The coefficient of static friction between the log and the ground is 0.50, and the coefficient of kinetic friction is 0.35. What minimum tension is required in the cable in order for the log to begin to slide?

Question 54

A 50-kg box is being pushed along a horizontal surface. The coefficient of static friction between the box and the ground is 0.65, and the coefficient of kinetic friction is 0.35. What horizontal force must be exerted on the box for it to accelerate at 1.2 m/s²?

A)60 N
B)120 N
C)170 N
D)230 N
E)490 N

Question 55

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 56

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A horizontal 140-N force is applied to the box. What is the friction force on the box?

A)140 N
B)160 N
C)16.5 N
D)0.00 N
E)42 N

Question 57

A policeman investigating an accident measures the skid marks left by a car on the horizontal road. He determines that the distance between the point that the driver slammed on the brakes (thereby locking the wheels)and the point where the car came to a stop was 28.0 m. From a reference manual he determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300. How fast was the car going when the driver applied the brakes?

A)10.7 m/s
B)12.8 m/s
C)21.4 m/s
D)32.9 m/s
E)45.7 m/s

Question 58

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 59

A baseball player is running to second base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.180, and the coefficient of static friction is 3.14. What is his speed when he reaches the plate?

A)4.47 m/s
B)2.89 m/s
C)1.96 m/s
D)2.56 m/s
E)He stops before reaching the plate.

Question 60

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 61

A driver in a $1000 - \mathrm { kg }$ car traveling at $24 \mathrm {~m} / \mathrm { s }$ slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the level road is 0.80, how long will the skid marks be?

A)37 m
B)30 m
C)46 m
D)34 m

Question 62

A 15-kg block is on a frictionless ramp that is inclined at 20° above the horizontal. It is connected by a very light string over an ideal pulley at the top edge of the ramp to a hanging 19-kg block, as shown in the figure. The string pulls on the 15-kg block parallel to the surface of the ramp. Find the magnitude of the acceleration of the 19-kg block after the system is gently released?

A)4.0 m/s²
B)3.8 m/s²
C)4.2 m/s²
D)4.5 m/s²

Question 63

Jason takes off 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 produce a forward thrust of 200 N and have a coefficient of kinetic friction with water of 0.10. Unfortunately, the skis run out of fuel after only 41 s. How far from his starting point has Jason traveled when he finally coasts to a stop?

A)3900 m
B)2900 m
C)2000 m
D)1400 m

Question 64

A system consisting of blocks, a light frictionless pulley, a frictionless incline, and very light connecting wires is shown in the figure. The wires pull on the left-hand blocks parallel to the surface of the ramp. The 9.0-kg block accelerates downward when the system is released gently from rest.
(a)What is the magnitude of the acceleration of the 9.0-kg block?
(b)What is the tension in the wire connecting the two blocks on the incline?

Question 65

The figure shows a block of mass m resting on a 20° slope. The block has coefficients of friction $\mu _ { \mathrm { S } } = 0.64$ and $\mu _ { \mathrm { k } } = 0.54$ with the surface of the slope. It is connected using a very light string over an ideal pulley to a hanging block of mass 2.0 kg. The string above the slope pulls parallel to the surface. What is the minimum mass m so the system will remain at rest when it is released from rest?

A)2.1 kg
B)3.3 kg
C)1.3 kg
D)3.6 kg

Question 66

You push downward on a trunk at an angle 25° below the horizontal with a force of $750 \mathrm {~N} .$ If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move?

A)81 kg
B)93 kg
C)73 kg
D)112 kg

Question 67

Jason takes off 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 produce a forward thrust of 200 N and have a coefficient of kinetic friction with water of 0.10. Unfortunately, the skis run out of fuel after only 90 s. What is Jason's top speed?

A)150 m/s
B)240 m/s
C)24 m/s
D)90 m/s

Question 68

You push horizontally on a 120-N box that is initially resting on a horizontal table. The coefficient of static friction between the box and the table is 0.75, and the coefficient of kinetic friction is 0.40. Find the friction force on the box if the push is equal to (a)84 N; (b)94 N.

Question 69

A 200-g hockey puck is launched at an initial speed of 16 m/s 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 µ_s = 0.40 and µ_k = 0.30, respectively. What vertical height does the puck reach above its starting point?

A)8.6 cm
B)17 cm
C)13 cm
D)4.2 cm

Question 70

As shown in the figure, block B on a horizontal tabletop is attached by very light horizontal strings to two hanging blocks, A and C. The pulleys are ideal, and the coefficient of kinetic friction between block B and the tabletop is 0.100. The masses of the three blocks are m_A = 12.0 kg, m_B = 7.00 kg, and m_C = 10.0 kg. Find the magnitude and direction of the acceleration of block B after the system is gently released and has begun to move.

Question 71

A 5.0-kg box slides on the surface on a ramp that rises at 37° above the horizontal. The coefficient of kinetic friction between the box and the surface of the ramp is 0.60. What are the magnitude and direction of the acceleration of the box if it is sliding (a)up the ramp, (b)down the ramp?

Question 72

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 0.40, at what rate does the box accelerate down the slope?

A)3.1 m/s²
B)3.4 m/s²
C)3.7 m/s²
D)4.1 m/s²

Question 73

A 2.8-kg tool can move on a perfectly smooth ramp that slants at 42° above the horizontal. What are the magnitude and direction of the acceleration of this tool if it is sliding (a)up the ram, (b)down the ramp?

Question 74

A 200-g hockey puck is launched up a ramp that is inclined at a 30° angle above the horizontal. The coefficients of static and kinetic friction between the puck and the ramp are µ_s = 0.40 and µ_k = 0.30, respectively, and the puck's initial velocity at the base is 3.8 m/s parallel to the sloping surface of the ramp. What speed does the puck have when it slides back down to its starting point?

Question 75

A flatbed truck is carrying a 20-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is 0.40, and the coefficient of kinetic friction is 0.30. What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?

A)0.38°
B)13°
C)17°
D)22°
E)68°

Question 76

A 150-N crate is being pulled up a perfectly smooth ramp that slopes upward at 15° by a pull that is directed at 30° above the surface of the ramp. What is the magnitude of the pull required to make the crate move up the ramp at a constant velocity of 1.75 m/s?

Question 77

A 7.5-kg stone moves up frictionless hill that slopes upward at 41° above the horizontal. If the stone has an initial velocity of 8.5 m/s at the bottom, how far (as measured along the surface of the hill)will it go before stopping?

Question 78

A slanted roof rises at 35° above the horizontal, and the straight-line distance from the top of the roof to the bottom edge is 4.5 m. The roof is covered with ice, so it offers no friction to objects sliding on it. A piece of ice at the top suddenly breaks loose and begins to slide down from rest.
(a)How long will it take for the ice to reach the bottom edge of the roof?
(b)How fast will the ice be traveling just as it reaches the bottom edge?

Question 79

The figure shows a system consisting of three blocks, a light frictionless pulley, and light connecting ropes that act horizontally on the upper two blocks. The 9.0-kg block is on a perfectly smooth horizontal table. The surfaces of the 12-kg block are rough, with µ_k = 0.30 between the 12-kg and 9.0-kg blocks. The mass M of the hanging block is set so that it descends at a constant velocity of 3.25 m/s.
(a)What is the mass M of the hanging block?
(b)The mass M is now changed to 5.0 kg, causing it to accelerate downward after it is released. What is the acceleration of the hanging mass?

Question 80

A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400, and the coefficient of kinetic friction is 0.300. What is the maximum acceleration that the truck can have if the crate is to stay in place relative to the truck?

A)3.92 m/s²
B)7.84 m/s²
C)8.00 m/s²
D)78.5 m/s²
E)196 m/s²