physics fun gravity

#14 AP MC Quiz Key DYNAMICS/CIRC. MOTION/GRAVITY 1. A hypothetical planet orbits a star with mass one-half the mass of our sun. The planet?s orbital radius is the same as the Earth?s. Approximately how many Earth years does it take for the planet to complete one orbit? A)1 2? B) 1 ?2? C) D) ?2 E) 2. An object shown in the accompanying figure moves in uniform circular motion. Which arrow best depicts the net force acting on the object at the instant shown? A. A B. B C. C D. D E. E 3. The ?reaction? force does not cancel the ?action? force because: A. The action force is greater than the reaction force. B. The action force is less than the reaction force. C. They act on different bodies. D. They are in the same direction.