Review Exam 2-New.doc - 1 - Physics 1401 - Exam 2 Chapter 5N-New 2. The second hand on a watch has a length of 4.50 mm and makes one revolution in 60.00 s. What is the speed of the end of the second hand as it moves in uniform circular motion? (a) 9.42 × 10-4 m/s (c) 5.34 × 10-3 m/s (e) 2.36 × 10-5 m/s (b) 2.67 × 10-3 m/s (d) 4.71 × 10-4 m/s 3. Approximately one billion years ago, the Moon orbited the Earth much closer than it does today. The radius of the orbit was only 24 400 km. Today, the radius is 385 000 km. The orbital period was only 23 400 s. The present period is 2.36 × 106 s. Assume that the orbit of the Moon is circular. Calculate the ratio of the speed of the Moon in its ancient orbit to the speed that it has today. (a) 15.8 (c) 10.2 (e) 6.39 (b) 12.8 (d) 7.15 5. A ball is whirled on the end of a string in a horizontal circle of radius R at constant speed v. The centripetal acceleration of the ball can be increased by a factor of 4 by (a) keeping the speed fixed and increasing the radius by a factor of 4. (b) keeping the radius fixed and increasing the speed by a factor of 4. (c) keeping the radius fixed and increasing the period by a factor of 4. (d) keeping the radius fixed and decreasing the period by a factor of 4. (e) keeping the speed fixed and decreasing the radius by a factor of 4. 7. A car traveling at 20 m/s rounds a curve so that its centripetal acceleration is 5 m/s2. What is the radius of the curve? (a) 4 m (c) 80 m (e) 640 m (b) 8 m (d) 160 mReview Exam 2-New.doc - 2 - 8. A satellite is placed in a circular orbit to observe the surface of Mars from an altitude of 144 km. The equatorial radius of Mars is 3397 km. If the speed of the satellite is 3480 m/s, what is the magnitude of the centripetal acceleration of the satellite? (a) 2.17 m/s2 (c) 2.99 m/s2 (e) 4.05 m/s2 (b) 2.60 m/s2 (d) 3.42 m/s2 11. A boy is whirling a stone around his head by means of a string. The string makes one complete revolution every second, and the tension in the string is FT. The boy then speeds up the stone, keeping the radius of the circle unchanged, so that the string makes two complete revolutions every second. What happens to the tension in the sting? (a) The tension is unchanged. (b) The tension reduces to half of its original value. (c) The tension increases to twice its original value. (d) The tension increases to four times its original value. (e) The tension reduces to one-fourth of its original value. 14. Sara puts a box into the trunk of her car. Later, she drives around an unbanked curve that has a radius of 48 m. The speed of the car on the curve is 16 m/s, but the box remains stationary relative to the floor of the trunk. Determine the minimum coefficient of static friction for the box on the floor of the trunk. (a) 0.42 (d) 0.33 (b) 0.54 (e) This cannot be determined without knowing the mass of (c) 0.17 the box. 15. In an amusement park ride, a small child stands against the wall of a cylindrical room that is then made to rotate. The floor drops downward and the child remains pinned against the wall. If the radius of the device is 2.15 m and the relevant coefficient of friction between the child and the wall is 0.400, with what minimum speed is the child moving if he is to remain pinned against the wall? (a) 7.26 m/s (c) 12.1 m/s (e) 9.80 m/s (b) 3.93 m/s (d) 5.18 m/sReview Exam 2-New.doc - 3 - 18. The maximum speed at which a car can safely negotiate an unbanked curve depends on all of the following factors except (a) the diameter of the curve. (b) the acceleration due to gravity. (c) the coefficient of static friction between the road and the tires. (d) the coefficient of kinetic friction between the road and the tires. (e) the ratio of the static frictional force between the road and the tires and the normal force exerted on the car. 20. Determine the minimum angle at which a roadbed should be banked so that a car traveling at 20.0 m/s can safely negotiate the curve if the radius of the curve is 2.00 × 102 m. (a) 0.200° (c) 11.5° (e) 78.2° (b) 0.581° (d) 19.6° Questions 23 through 25 pertain to the statement below: A 1000-kg car travels along a straight 500-m portion of highway (from A to B) at a constant speed of 10 m/s. At B, the car encounters an unbanked curve of radius 50 m. The car follows the road from B to C traveling at a constant speed of 10 m/s while the direction of the car changes from east to south. 23. What is the magnitude of the acceleration of the car as it travels from A to B? (a) 2 m/s2 (c) 10 m/s2 (e) zero m/s2 (b) 5 m/s2 (d) 20 m/s2 24. What is the magnitude of the acceleration of the car as it travels from B to C? (a) 2 m/s2 (c) 10 m/s2 (e) zero m/s2 (b) 5 m/s2 (d) 20 m/s2 25. What is the magnitude of the frictional force between the tires and the road as the car negotiates the curve from B to C? (a) 20 000 N (c) 5000 N (e) 1000 N (b) 10 000 N (d) 2000 NReview Exam 2-New.doc - 4 - 26. The earth exerts the necessary centripetal force on an orbiting satellite to keep it moving in a circle at constant speed. Which statement best explains why the speed of the satellite does not change although there is a net force exerted on it? (a) The satellite is in equilibrium. (b) The acceleration of the satellite is zero m/s2. (c) The centripetal force has magnitude mv2/r. (d) The centripetal force is canceled by the reaction force. (e) The centripetal force is always perpendicular to the velocity. 30. A satellite is placed in equatorial orbit above Mars, which has a radius of 3397 km and a mass MM = 6.40 × 1023 kg. The mission of the satellite is to observe the Martian climate from an altitude of 488 km. What is the orbital period of the satellite? (a) 9.18 × 102 s (c) 7.36 × 103 s (e) 7.27 × 1012 s (b) 3.62 × 103 s d) 1.08 × 105 s 45. A 25-kg box is sliding down an ice-covered hill. When it reaches point A, the box is moving at 11 m/s. Point A is at the bottom of a circular arc that has a radius R = 7.5 m. What is the magnitude of the normal force on the box at Point A? (a) 250 N (d) 650 N (b) …