Part (a) A planet orbits a star in a circular orbit at a constant orbital speed. Which of the following statements is true? MultipleChoice 1) The planet experiences no centripetal force. 2) None of these are correct. 3) All of these are correct, 4) The planet experiences a centripetal force pulling towards its star. 5) The magnitude of the orbital velocity of the planet is unchanged, thus there is no acceleration and therefore no force is acting on the planet. 6) The planet experiences a centripetal force pushing it away from its star. Part (b) When a planet is orbiting a star, which force plays the role of the centripetal force? MultipleChoice : 1) The force resulting from the planet's velocity around the star. 2) The force resulting from the centripetal acceleration. 3) The gravitational force. Part (c) Which of the following statements about uniform circular motion is true? MultipleChoice !) None of these choices are true. 2) An object in uniform circular motion experiences a centripetal force and a tangential force. 3) An object in uniform circular motion experiences a tangential force. 4) An object in uniform circular motion experiences a centripetal force, 5) An object in uniform circular motion experiences a centripetal force, an equal and opposite centrifugal force, and a tangential force, 6) An object in uniform circular motion experiences no forces. Part (d) A student swings a ball on a string in a circle at a constant speed, then suddenly lets go of the string. When the student lets go of the string. what happens from a physics standpoint? MultipleChoice 1) A tangential force stops acting on the ball 2) None of these are correct, 3) Nothing happens from the standpoint of physics. 4) The centripetal force disappears 5) A centripetal force starts acting on the ball. 6) A tangential force starts acting on the ball