Problems on Application of Newton's Laws

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College Physics, 2e (Knight)
Chapter 5 Applying Newton's Laws

5.1 Quantitative

1) A fish is to be weighed at the harbor. If the mass of the fish is 69.0 kg, what will be the reading on the scale? (Use g = 9.8 m/s2.) A) 676 N
B) 7.04 N
C) 7.74 N
D) 744 N
Answer: A
Var: 50+

2) A skydiver reaches a "terminal velocity" of 120 km/h. If the skydiver has a mass of 59.0 kg, what is the magnitude of the upward force on the skydiver due to wind resistance? (Use g = 9.8 m/s2.)

A) 578 N
B) 6.02 N
C) 5.42 N
D) 636 N
Answer: A
Var: 50+

3) A person with a mass of 78 kg is riding in an elevator that is accelerating upward at 1.80 m/s2. What is the person's apparent weight? (Use g = 9.8 m/s2.) A) 900 N
B) 760 N
C) 620 N
D) 960 N
Answer: A
Var: 35

4) A 80 N force is needed to slide a 50.0 kg box across a flat surface at a constant velocity. What is the coefficient of kinetic friction between the box and the floor? (Use g = 9.8 m/s2.) A) 0.16

B) 0.13
C) 0.15
D) 0.18
Answer: A
Var: 50+

5) A piano mover raises a 100 kg piano at a constant rate using a frictionless pulley system, as shown in the figure. With roughly what force is the mover pulling down on the rope?

[pic]

A) 2000 N
B) 1000 N
C) 500 N
D) 250 N
E) Depends on the velocity!
Answer: C
Var: 1

6) An object at rest on an inclined plane starts to slide when the incline angle is increased to 17°. What is the coefficient of static friction between the object and the incline? (Use g = 9.8 m/s2.) A) 0.31

B) 0.27
C) 0.33
D) 0.37
Answer: A
Var: 31

7) 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? (Use g = 9.8 m/s2.) A) 4.7 m/s2

B) 5.2 m/s2
C) 5.5 m/s2
D) 6.2 m/s2
Answer: A
Var: 50+

8) Starting from rest, a 75 kg skier slides down a 17.0° slope. If the coefficient of kinetic friction between the skis and snow is 0.120 and it takes 16.9 s to get to the bottom, how long is the ski trail? (Use g = 9.8 m/s2.) A) 248 m

B) 496 m
C) 124 m
D) 186 m
Answer: A
Var: 50+

[pic]

9) Dick and Jane stand on a platform of negligible weight, as shown in the figure. Dick weighs 500 N and Jane weighs 400 N. Jane is supporting some of her weight on the end of the rope she is holding. What is the downward force she is exerting on the platform? A) 0

B) 50 N
C) 100 N
D) 240 N
E) 300 N
Answer: C
Var: 1

10) You push downward on a trunk at an angle 25° below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction is 0.76, what is the most massive trunk you will be able to move? (Use g = 9.8 m/s2.) A) 59 kg

B) 68 kg
C) 54 kg
D) 82 kg
Answer: A
Var: 31

11) Jason takes off across level water on his jet-powered skis. The combined mass of Jason and skis is 75 kg (the mass of the fuel is negligible). The skis have a thrust of 200 N and a coefficient of kinetic friction on water of 0.1. 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
Answer: A
Var: 50+

12) Kieran takes off down a 50 m high, 10° slope on his jet-powered skis. The skis have a thrust of 280 N. The combined mass of skis and Kieran is 50kg (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
Answer: A
Var: 34

[pic]

13) A 6.0 kg box is held at rest by two ropes that form 30° angles with the vertical. An external force F acts vertically downward on the box. The force exerted by each of the two ropes is denoted by T. A force diagram, showing the four forces that act on the box in equilibrium, is shown in the figure. The magnitude of force F is 410 N. The magnitude of force T is closest to: A) 271 N

B) 235 N...
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