Physics 011

A of PQ#5

Chapter 5: Circular Motion; Gravitation
Practice Questions

 1. A stone, of mass m, is attached to a strong string and whirled in a vertical circle of radius r. At the exact top of the path the tension in the string is 3 times the stone's weight. The stone's speed at this point is given by The correct answer: 2. A stone, of mass m, is attached to a strong string and whirled in a vertical circle of radius r. At the exact bottom of the path the tension in the string is 3 times the stone's weight. The stone's speed at this point is given by  The correct answer: The tension and the weight are in opposite directions. Review Example 5-5 in Giancoli. 3. A stone is whirled in a vertical circle on a cord. Halfway up The correct answer: the tension force is towards the center of the circle and the weight is down. 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 the track at the top of the loop, what is the minimum value for its centripetal acceleration at this point? The correct answer: g downward 5. A girl attaches a rock to a string, which she then swings counter- clockwise in a horizontal circle. The string breaks at point P on the sketch, which shows a bird's-eye view (i.e., as seen from above). What path will the rock follow? The correct answer: B Review section 5-2 of Giancoli. 6. The following statements refer to man-made, artificial satellites in orbit around earth. Which is an accurate statement?  The correct answer: A satellite in a large diameter circular orbit will always have a longer period of revolution about the earth than will a satellite in a smaller circular orbit. Review Section 5-8 in Giancoli. 7. Two objects are travelling in circular orbits. Object A is travelling at twice the velocity of object B in a circle with a diameter of twice that of B. The centripetal acceleration  The correct answer: of A is twice that B. The speed is squared the radius is not. Review Section 5-2 in Giancoli. 8. A cannon ball is fired horizontally off a high cliff over a great distance. If air resistance can be ignored the path it follows is The correct answer: part of an ellipse. 9. The variation of g over the surface of the earth does not depend upon  The correct answer: rotation of the Earth. The earth is not a sphere. Review Section 5-7 in Giancoli. 10. There are four forces in nature. Which one allows you to close a door by pushing on it?  The correct answer: Electric Gravity is always attractive. Review Section 5-10 in Giancoli. 11. A ball of mass m is moving in a circle with uniform speed on a horizontal surface with friction at the end of a radial metal rod. The net force is The correct answer: is along the rod. 12. Two bodies of equal mass are separated by a distance R. If you double the distance between them the new gravitational force will be  The correct answer: one fourth the old force. The force decreases with distance. Review Section 5-6 in Giancoli. 13. Two bodies of equal mass are separated by a distance R. If you double each mass then the new force will be  The correct answer: four times the old force. Remember both masses are increasing. Review Section 5-6 in Giancoli. 14. Two bodies of equal mass are separated by a distance R. If you double one mass then the new force will be The correct answer: twice the old force. 15. Two bodies of equal mass are separated by a distance R. If you double each mass and double the distance between them, the new force will be  The correct answer: the same as the old force. Review Section 5-6 in Giancoli. 16. The Earth moves faster in the winter when its closest to the Sun. This is an example of  The correct answer: Kepler's Second Law. Review Section 5-9 in Giancoli. 17. Which of the following does not belong with the others?  The correct answer: A car coasts down a road at constant speed. The car is accelerating. Review Section 5-1 in Giancoli. 18. Kepler's Third Law can be used to relate the motions of the  The correct answer: Moon and the Space Shuttle. The Moon is a satellite of the Earth. Review Section 5-9 in Giancoli. 19. If the mass of the earth was quadrupled and nothing else was changed  The correct answer: g would increase by a factor of 4. Review Section 4-7 in Giancoli. 20. A planet with twice the mass and twice its radius has a value of g Your answer: 1/2 that of Earth. 21. Four equal masses are arranged in a perfect square. The direction of the force on the one in the lower left hand corner  The correct answer: is at 45 degrees. Gravity is an attractive force. Review Section 5-6 in Giancoli. 22. Four equal masses are arranged in a perfect square. The magnitude of the force on the one in the lower left hand corner due to the one diagonally across from it  The correct answer: would be half the magnitude of the force from either of the other two masses. It would be less than either. Review Section 5-6 in Giancoli. 23. The speed of a satellite in orbit does not depend on  The correct answer: its mass. The force of gravity depends upon this. Review Section 5-6 in Giancoli. 24. The period of planet X is .62 Earth years and that of planet Y is 1.9 years.  The correct answer: The Earth is between planet X and planet Y. Review Example 5-16 in Giancoli. 25. Which of the following does not belong with the others?  The correct answer: A person standing on a scale.