PHY 241
Chapters 12 & 13: Quiz 1
1. An astronaut is on a 100 m life-line outside a space-ship, circling the ship with an angular velocity of 0.1 rad/s. How far can she be pulled in before the centripetal acceleration reaches 5g = 49 m/s²?
10.1 m
50.0 m
72.7 m
89.9 m
2. A heavy bank vault door is opened by the application of a force of 300 N directed perpendicular to the door and 0.8 m from the hinges. What is the torque due to this force about an axis through the hinghes?
120 N-m
240 N-m
300 N-m
360 N-m
3. A uniform bridge span weights 50 x 10³ N and is 40.0 m long. An automobile weights 15 x 10³ N is parked with its center of gravity located 12.0 m from the right pier. What upward support force is provided by the left pier?
29.5 x 10³ N
35.5 x 10³ N
65.0 x 10³ N
32.5 x 10³ N
4. A 20 kg child wants to use a 10 kg board that is 4.0 m long as a seesaw. Since all her friends are busy, she decides to seesaw by herself by putting the support at the center of gravity when she sits on one end of the board. How far from her will the support point be?
2.0 m
1.0 m
0.67 m
0.33 m
5. A 80 kg man is one fourth of the way up a 10 m ladder that is resting against a smooth, frictionless wall. If the ladder is 20 kg and it makes an angle of 60º with the ground, find the force of friction of the ground on the foot of the ladder.
816 N
228 N
82 N
170 N
6. A 100 N uniform ladder of length 8 m rests against a smooth vertical wall. If the coefficient of static friction between ladder and floor is 0.40, what is the minimum angle that the ladder can make with the floor before it slips?
22º
51º
18º
42º
7. A meter stick is supported by a knife angle at the 50 cm mark and has masses of 0.40 and 0.60 kg hanging from the 20 cm and 80 cm marks, respectively. Where should a third mass of 0.30 kg be hung to keep a stick balanced?
20 cm
70 cm
30 cm
25 cm
8. An 800 N billboard worker stands on a 4 m scaffold supported by vertical ropes at each end. If the scarffold weighs 500 N and the worker stands 1 m from one end, what is the tension in the rope nearest the worker?
450 N
500 N
800 N
850 N
9. If a force of 50 N stretches a spring 0.10 m, what is the spring constant of the spring?
5.0 N/m
500 N/m
0.002 N/m
0.25 N/m
10. A 0.2 kg object is suspended from a spring with spring constant, k = 10 N/m, and moves with simple harmonic motion. At the instant that it is displaced from equilibrium by -0.05 m, what is its acceleration?
1000 m/s²
40 m/s²
0.1 m/s²
2.5 m/s²
11. A 0.2 kg object is suspended from a spring with a spring constant of k = 10 N/m. The object moves with simple harmonic motion and has an amplitude of 0.80 m. What is the potential energy of the system when the object displacement is 0.08 m?
0.40 J
zero
3.2 x 10-² J
62.5 J
12. A 0.2 kg object, suspended from a spring with a spring constant of k = 10 N/m, is moving in simple harmonic motion and has an amplitude of 0.08 m. What is its velocity at the instant when its displacement is 0.04 m? (Hint: Use conservation of energy.)
9.8 m/s
4.9 m/s
49.0 cm/s
24.5 cm/s
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