Circular Motion Test Review

Transcription

1 Circular Motion Test Review Name: Date: 1) Is it possible for an object moving with a constant speed to accelerate? Explain. A) No, if the speed is constant then the acceleration is equal to zero. B) No, an object can accelerate only if there is a net force acting on it. C) Yes, although the speed is constant, the direction of the velocity can be changing. D) Yes, if an object is moving it can experience acceleration 2) An object moves in a circular path at a constant speed. Compare the direction of the object's velocity and acceleration vectors. A) Both vectors point in the same direction. B) The vectors point in opposite directions. C) The vectors are perpendicular. D) The question is meaningless, since the acceleration is zero. 3) What force is needed to make an object move in a circle? A) kinetic friction B) static friction C) centripetal force D) weight 4) A roller coaster car is on a track that forms a circular loop in the vertical plane. If the car is to just maintain contact with track at the top of the loop, what is the minimum value for its centripetal acceleration at this point? A) g downward B) 0.5g downward C) g upward D) 2g upward Page 1

2 5) A car goes around a curve of radius r at a constant speed v. What is the direction of the net force on the car? A) toward the curve's center B) away from the curve's center C) toward the front of the car D) toward the back of the car 6) A boy and a girl are riding on a merry-go-round which is turning at a constant rate. The boy is near the outer edge, and the girl is closer to the center. Who has the greater angular displacement? A) the boy B) the girl C) Both have the same non-zero angular displacement. D) Both have zero angular displacement. 7) Two objects attract each other gravitationally. If the distance between their centers is cut in half, the gravitational force A) is cut to one fourth. B) is cut in half. C) doubles. D) quadruples 8) Compared to its mass on the Earth, the mass of an object on the Moon is A) less. B) more. C) the same. D) half as much. Page 2

3 9) A boy and a girl are riding on a merry-go-round which is turning at a constant rate. The boy is near the outer edge, and the girl is closer to the center. Who has the greater linear speed? A) the boy B) the girl C) Both have the same non-zero translational velocity. D) Both have zero translational velocity. 10) An object moves with a constant speed of 30 m/s on a circular track of radius 150 m. What is the acceleration of the object? A) zero B) 0.17 m/s2 C) 5.0 m/s2 D) 6.0 m/s2 11) What is the centripetal acceleration of a point on the perimeter of a bicycle wheel of diameter 70 cm when the bike is moving 8.0 m/s? A) 91 m/s2 B) m/s2 C) m/s2 D) m/s2 12) How many revolutions per minute must a circular, rotating space station of radius 1000 m rotate to produce an artificial gravity of 9.80 m/s2? A) 0.65 rpm B) 0.75 rpm C) 0.85 rpm D) 0.95 rpm Page 3

4 13) A bicycle wheel rotates uniformly through 2.0 revolutions in 4.0 s. What is the frequency of the wheel's rotation? A) 0.50 Hz B) 1.0 Hz C) 2.0 Hz D) 4.0 Hz 14) A 0.50-kg mass is attached to the end of a 1.0-m string. The system is whirled in a horizontal circular path. If the maximum tension that the string can withstand is 350 N. What is the maximum speed of the mass if the string is not to break? A) 700 m/s B) 26 m/s C) 19 m/s D) 13 m/s 15) A kg mass, attached to the end of a m string, is whirled around in a smooth level table. If the maximum tension that the string can withstand is 250 N, then what maximum linear speed can the mass have if the string is not to break? A) 19.4 m/s B) 22.4 m/s C) 25.0 m/s D) 32.7 m/s 16) A wheel of diameter 26 cm turns at 1500 rpm. How far will a point on the outer rim move in 2.0 s? A) 3.1 m B) 41 m C) 90 m D) 180 m Page 4

5 17) A pilot makes an outside vertical loop (in which the center of the loop is beneath him) of radius 3200 m. At the top of his loop he is pushing down on his seat with only one-half of his normal weight. How fast is he going? A) 5.0 m/s B) 25 m/s C) 125 m/s D) 625 m/s 18) A car is negotiating a flat curve of radius 50 m with a speed of 20 m/s. The centripetal force provided by friction is N. What is the mass of the car? A) 500 kg B) 1000 kg C) 1500 kg D) 2000 kg 19) A car goes around a flat curve of radius 50 m at a speed of 14 m/s. What must be the minimum coefficient of friction between the tires and the road for the car to make the turn? A) 0.20 B) 0.40 C) 0.60 D) ) A car traveling 20 m/s rounds an 80-m radius horizontal curve with the tires on the verge of slipping. How fast can this car round a second curve of radius 320 m? (Assume the same coefficient of friction between the car's tires and each road surface.) A) 20 m/s B) 40 m/s C) 80 m/s D) 160 m/s Page 5

6 21) A wheel of radius 1.0 m is rotating with a constant angular speed of 2.0 rad/s. What is the linear speed of a point on the wheel's rim? A) 0.50 m/s B) 1.0 m/s C) 2.0 m/s D) 4.0 m/s 22) What minimum banking angle is required for an Olympic bobsled to negotiate a 100-m radius turn at 35 m/s without skidding? (Ignore friction.) A) 31 B) 41 C) 51 D) 61 23) A curve of radius 80 m is banked at 45. Suppose that an ice storm hits, and the curve is effectively frictionless. What is the safe speed with which to take the curve without either sliding up or down? A) 9.4 m/s B) 28 m/s C) m/s D) The curve cannot be taken safely. 24) The mass of the Moon is kg and its mean radius is km. What is the acceleration due to gravity at the surface of the Moon? A) m/s2 B) 9.80 m/s2 C) 1.6 m/s2 D) 0.80 m/s2 Page 6

7 25) By how many newtons does the weight of a 100-kg person change when he goes from sea level to an altitude of 5000 m? (The mean radius of the Earth is m.) A) 0.6 N B) 1.6 N C) 2.6 N D) 3.6 N 26) A wheel starts at rest, and has an angular acceleration of 4 rad/s2. Through what angle does it turn in 3.0 s? A) 36 rad B) 18 rad C) 12 rad D) 9.0 rad 27) A wheel of diameter of 68.0 cm slows down uniformly from 8.40 m/s to rest over a distance of 115 m. What is the total number of revolutions the wheel rotates in coming to rest? A) 53.8 rev B) 26.9 rev C) 338 rev D) 169 rev 28) A wheel of diameter of 68.0 cm slows down uniformly from 8.40 m/s to rest over a distance of 115 m. What is the angular acceleration? A) rad/s2 B) rad/s2 C) rad/s2 D) rad/s2 Page 7

8 29) Angular displacement is usually express in units of A) meters. B) radians. C) revolutions. D) arcs. 30) A pulsar (a rotating neutron star) emits pulses at a frequency of 0.40 khz. The period of its rotation is A) 2.5 ms. B) 2.5 s. C) s. D) 25 ms. Page 8