Chapter 7 & 8 Prep Test: Circular Motion and Gravitation Multiple Choice Identify the choice that best completes the statement or answers the question. A monkey rides a tricycle in a circular path with a radius of 3.0 m. The tangential speed of the tricycle is 2.0 m/s. The combined mass of the tricycle and the monkey is 30. kg. 1 What is the magnitude of the centripetal force on the tricycle? A 1.3 N B 40. N C.66 N D 3.7 N 2 What is the magnitude of the tricycle s centripetal acceleration? A 1.3 m/s 2 B 40. m/s 2 C.66 m/s 2 D 1.0 m/s 2 3 A planet has a mass of 6.4 x 10 23 kg and its moon has a mass of 9.6 x 10 15 kg. If the magnitude of the gravitational force between the two bodies is 4.6 x 10 15 N, how far apart are the planet and its moon? A 9.402 x 10 3 km B 8.84 x 10 7 km C 9.4 x 10 3 m D 9.4 x 10 3 km figure 7-3: The object is rotating clockwise and is located at point S. Line SP is tangent to the circular motion. Line SH is the radius of the circle. 4 Consider figure 7-3. Which way is the centripetal force directed? A towards H B away from H C see MrH 5 Consider figure 7-3. Which way is the centripetal acceleration directed? A towards H C towards S B away from H D away from S 6 Consider figure 7-3. Which way is the tangential speed directed? A towards H B towards P C towards S 1
7 Car mechanics put wheels on by tightening the lug nuts with pneumatic tools. If you need to change a flat tire and cannot exert enough force to loosen a lug nut with a wrench, which of the following should you do? A Use a wrench with a longer handle. B Use a wrench with a shorter handle. C You should exert a force on the wrench closer to the bolt. D Tie a rope to the end of the wrench and pull on the rope. 8 The centripetal force on a car taking a left turn is A in the direction opposite the centripetal acceleration. B in the same direction as the centripetal acceleration. C in the same direction as the tangential speed. D in the direction opposite the tangential speed. 9 If gravitation is a weak force, why is it such a significant force on Earth? A The moon has a smaller mass than the Earth. B The Earth s mass is large. C Objects on the surface are far from the center of the Earth. D The universal gravitational constant increases in proportion with the mass of an object. E The Earth s mass is small. 10 What kind of simple machine are you using if you wheel a heavy object up a ramp instead of using the stairs? A wedge B pulley C screw D inclined plane 11 What is the force of attraction between a 50.0 kg girl and a 68.0 kg boy who are standing 2 m apart? A 9.81 N D 2.27 x 10-7 N B 1.13 x 10-7 N E they have no attraction C 5.67 x 10-8 N 12 2006 RH120 is a tiny near-earth asteroid with a diameter of about 5 meters and it was in Earth orbit from September 2006 to June 2007. While the asteroid was in orbit, the force acting on the asteroid A was zero. B was pointed in the direction that the satellite was moving. C was increasing. D was pointed toward the center of Earth at all times. 13 The gravitational force between two masses is 36 N. What is the gravitational force if the distance between them is quadrupled (increased by a factor of four)? A 9.0 N B 140 N C 2.3 N D 0 N 14 A student stands on a scale in an elevator when the cable breaks and the elevator free-falls to the Earth. While the elevator plummets, the student would appear to be weightless, this is because A the net gravitational force on the student is zero. B no gravitational forces act on the student. C no forces act on the student. D the net gravitational force on the student is not balanced by a normal force. 2
15 What will produce the greatest reduction in the gravitational force between the two objects? A reducing the distance between the masses by half B reducing one mass by half C doubling one mass D doubling the distance between the masses 16 When an object traveling in a circular path loses its centripetal force, it will travel in a straight line because of A inertia. C centrifugal force. B centripetal acceleration. D tangential force. 17 When an object is moving with uniform circular motion, the object s tangential speed A is constant. C is perpendicular to the plane of motion. B is directed toward the center of motion. D is circular. 18 When calculating gravitational force, you should measure the radius A from the closest points on each body. B from the center of each body. C from the most distant points on each body. D from the center of one body to the closest point on the other body. 19 Which object can provide centripetal force? A friction B gravity C tension D all are correct 20 Centripetal force is A not required for all turns B tangent to the motion of the object C net force directed toward the center of an object s circular path D perpendicular to the centripetal acceleration 21 Cheyenne Mountain nuclear bunker has the Alternative Command Center for the North American Aerospace Defense Command (NORAD). NORAD is a combined organization of the United States and Canada that provides aerospace warning, air sovereignty, and defense for North America. Cheyenne Mountain was designed for a 30 megaton nuclear explosion within 1.2 mi (1.9 km). The 25-ton North blast door is the main entrance. If the door is opened by the application of a force of 4.0 10 2 N directed perpendicular to the plane of the door at a distance of 9.0 m from the hinges. What is the torque? A 3600 N m B 2400 N m C 3000 N m D 1200 N m 22 If a lever arm is cut in half, how much force will be required to obtain the same amount of torque? A two times as much C four times as much B one-half as much D one-fourth as much 3
Spiraled Questions Identify the one choice that best completes the statement or answer the question. v x t F ma 23 A students does an experiment to measure the height of the bleachers by measuring the time it takes for the penny to fall from the top. The calculated height is 2 meters less than the actual height. The reason for this variation is most likely due to A local flucuations in gravity. C air resistance. B the mass of the object. D human error. 24 An object moves 11m in 1.0s. What is the average speed of the object? A 6.1 m B 11 s m C 6.6 s m s D 5.5 m s 25 A 20 kg boy is out walking his dogs. One dog pulls him to the left with a force of 70N and the other pulls him to the right with a force of 10N. What is the acceleration of the man? A 6 m B 3 m C 2 m D 4 m s 2 s 2 s 2 s 2 26 What would the distance vs time graph look like for an object moving at constant speed? A horzontal line C straight line with non-zero slope B parbolic curve D what s a graph? 27 The graph below shows the velocity of a car that is moving in a straight line. During which of the following intervals are forces on the car balanced? A A to B C C to D B B to C D G to H 4
28 A red-blooded, All-American football player kicks a 0.43 kilogram football with a force of 270 newtons. What is the force on the player s foot? A 6.3 N C 270 N B 5.279 N D 0.43 N 29 A student attempts to measure the mass of a kitten by measuring the force required to accelerate it at 1 m/s 2 on a level surface. the force required is 2N, and the student concludes that the kitten has a mass of 2 kg. A balance shows that the mass of the kitten is really 1.5 kg. The experimental error is most likely due to A gravity. B friction. C work. D inertia. E dogs 5