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# Physics -- Circular Motion & Gravitation Study Guide

By Jennifer Robertson,2014-06-02 20:45
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Physics -- Circular Motion & Gravitation Study Guide

Physics -- Circular Motion & Gravitation Study Guide

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____ 1. When an object is moving with uniform circular motion, the object’s tangential speed

a. is circular.

b. is perpendicular to the plane of motion.

c. is constant.

d. is directed toward the center of motion.

____ 2. When an object is moving with uniform circular motion, the centripetal acceleration of the object

a. is circular.

b. is perpendicular to the plane of motion.

c. is zero.

d. is directed toward the center of motion.

____ 3. What is the term for the net force directed toward the center of an object’s circular path?

a. circular force c. centripetal force

b. centrifugal force d. orbital force

____ 4. Which of the following can be a centripetal force?

a. friction c. tension

b. gravity d. all of the above

A child rides a bicycle in a circular path with a radius of 2.0 m. The tangential speed of the bicycle is 2.0 m/s.

The combined mass of the bicycle and the child is 43 kg.

____ 5. What is the magnitude of the bicycle’s centripetal acceleration? 2 2 a. 1.0 m/sc. 4.0 m/s2 2 b. 2.0 m/sd. 8.0 m/s

____ 6. When a car makes a sharp left turn, what causes the passengers to move toward the right side of the car?

a. centripetal acceleration c. centrifugal force

b. centripetal force d. inertia

____ 7. A ball is whirled on a string, then the string breaks. What causes the ball to move off in a straight line?

a. centripetal acceleration c. centrifugal force

b. centripetal force d. inertia

____ 8. Tides are caused by

a. differences in the gravitational force of the sun at different points on Earth.

b. differences in the gravitational force of the moon at different points on Earth.

c. differences in Earth’s gravitational field strength at different points on Earth’s surface.

d. fluctuations in the gravitational attraction between Earth and the moon.

____ 9. Why does an astronaut weigh less on the moon than on Earth?

a. The astronaut has less mass on the moon.

b. The astronaut is farther from Earth’s center when he or she is on the moon.

c. The gravitational field strength is less on the moon’s surface than on Earth’s surface.

d. The astronaut is continually in free fall because the moon orbits Earth.

____ 10. If you lift an apple from the ground to some point above the ground, the gravitational potential energy in the

system increases. This potential energy is stored in

a. the apple.

b. Earth.

c. both the apple and Earth.

d. the gravitational field between Earth and the apple.

____ 11. In this text, which of the following symbols represents gravitational field strength?

a. c. g F

b. G d. F

____ 12. In this text, which of the following symbols represents the constant of universal gravitation?

a. c. g F

b. G d. F

____ 13. Which of the following equations expresses Newton’s law of universal gravitation?

a. c.

b. d.

____ 14. When calculating the gravitational force between two extended bodies, you should measure the distance

a. from the closest points on each body.

b. from the most distant points on each body.

c. from the center of each body.

d. from the center of one body to the closest point on the other body.

____ 15. The gravitational force between two masses is 36 N. What is the gravitational force if the distance between

them is tripled? (G = 6.673 10 Nm/kg)

a. 4.0 N c. 18 N

b. 9.0 N d. 27 N

____ 16. Kepler developed his laws of planetary motion as he tried to reconcile

a. Ptolemaic theory with Copernican theory.

b. Ptolemaic theory with Copernicus’s data.

c. Copernican theory with Tycho Brahe’s data.

d. Copernican theory with his own data.

____ 17. Until the middle of the 16th century, most people believed ____ was at the center of the universe.

a. Earth c. the sun

b. the moon d. a black hole

____ 18. In the figure above, according to Kepler’s laws of planetary motion,

a. c. A = A. if t;= t, then the orbit is circular.

b. d. t;> t. if t;= t, then A = A.

____ 19. Newton’s law of universal gravitation

a. is equivalent to Kepler’s first law of planetary motion.

b. can be used to derive Kepler’s third law of planetary motion.

c. can be used to disprove Kepler’s laws of planetary motion.

d. does not apply to Kepler’s laws of planetary motion.

____ 20. The equation for the speed of an object in circular orbit is . What does m represent in this

equation?

a. the mass of the sun c. the mass of the central object

b. the mass of Earth d. the mass of the orbiting object

____ 21. When an astronaut in orbit experiences apparent weightlessness,

a. no forces act on the astronaut.

b. no gravitational forces act on the astronaut.

c. the net gravitational force on the astronaut is zero.

d. the net gravitational force on the astronaut is not balanced by a normal force.

____ 22. What term describes a change in the speed of an object in circular motion?

a. tangential speed c. centripetal acceleration

b. tangential acceleration d. centripetal force

23. On what variable factors do the period and speed of an object in circular orbit depend?

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Problem

A 35 kg child moves with uniform circular motion while riding a horse on a carousel. The horse is 3.2 m from

the carousel’s axis of rotation and has a tangential speed of 2.6 m/s.

25. What is the child’s centripetal acceleration?

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26. What is the centripetal force on the child?

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27. A 61.5 kg student sits at a desk 1.25 m away from a 70.0 kg student. What is the magnitude of the

gravitational force between the two students? (G = 6.673 10 Nm/kg)

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28. Two trucks with equal mass are attracted to each other with a gravitational force of 6.7 10 N. The trucks

are separated by a distance of 3.0 m. What is the mass of one of the trucks? (G = 6.673 10 Nm/kg)

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A new planet is discovered orbiting a star with a mass 3.5 10 kg at a distance of 1.2 10 m. Assume

that the orbit is circular.

29. What is the orbital period of the planet? (G = 6.673 10 Nm/kg)

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30. Earth’s mean distance from the sun is 1.50 10 m. The length of one Earth year is 3.16 10 s. Use this

data to calculate the mass of the sun. (G = 6.673 10 Nm/kg)

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