Question 1

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

Accepted Answer

A)  exactly 2.0 N. 
B)  exactly 1.0 N 
C)  0.50 N 
D)  0.00 N 
E)  more than 19.6 N 
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 2

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?

Accepted Answer

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

Question 3

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.

Accepted Answer

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

Question 4

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?

Accepted Answer

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

Question 5

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?

Accepted Answer

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. 
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 6

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?

Accepted Answer

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 
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 7

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 µk = 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?

Accepted Answer

(a) 3.6 kg

Question 8

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?

Accepted Answer

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

Question 9

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?

Accepted Answer

The answer of A 7.5-kg stone moves up frictionless hill...

Question 10

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?

Accepted Answer

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

Question 11

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?

Accepted Answer

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

Question 12

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?

Accepted Answer

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

Question 13

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?

Accepted Answer

(a) 1.3 s

Question 14

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?

Accepted Answer

The answer of A 30.0-kg load is being held in...

Question 15

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

Accepted Answer

A)  50° 
B)  40° 
C)  33° 
D)  65° 
E)  45° 
A)  50° 
B)  40° 
C)  33° 
D)  65° 
E)  45°

Question 16

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?

Accepted Answer

(a) 190 N

Question 17

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?

Accepted Answer

The answer of A 55-kg box rests on a horizontal...

Question 18

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?

Accepted Answer

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

Question 19

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?

Accepted Answer

A)  0.38° 
B)  13° 
C)  17° 
D)  22° 
E)  68° 
A)  0.38° 
B)  13° 
C)  17° 
D)  22° 
E)  68°

Question 20

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?

Accepted Answer

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 
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

Exam 5: Applying Newtons Laws

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

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?

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.

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?

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 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?

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 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?

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 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 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?

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

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?

A driver in a 1000−kg1000 - \mathrm { kg }1000−kg car traveling at 24 m/s24 \mathrm {~m} / \mathrm { s }24 m/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 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?

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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?