Name Physics Test 7: Circular Motion page 1 hmultiple Choice Read each question and choose the best answer by putting the corresponding letter in the blank to the left. 1. The SI unit of angular speed is A. rad/min. B. s 1. C. radians. D. m/s. 2. If a girl s speed on a merry-go-round is constant, the girl s instantaneous acceleration A. is parallel to the center of her circular path. B. is away from the center of her path. C. is toward the center of her path. D. follows the arc of her path. 3. In an accelerated reference frame, which of the vectors is not perpendicular to centripetal acceleration at any given instant? A. position vector B. tangential velocity C. angular velocity D. angular acceleration 4. What is the acceleration of a car going 25.0 m/s on a curved entrance ramp to an interstate? The ramp s curve has a radius of 45.0 m. A. 14.0 m/s 2 B. 139 m/s 2 C. 0.555 m/s 2 D. 0.720 m/s 2 5. Angular acceleration only applies to systems in which A. there is nonuniform circular motion. B. angular velocity is constant. C. centripetal acceleration is nonzero. D. angular speed is constant. 6. The force needed to keep a body moving in a circular path is A. centrifugal force. B. directly proportional to its speed. C. inversely proportional to the mass of the body. D. centripetal force.
Physics Test 7: Circular Motion page 2 7. Which statement about torque is not true? A. An unbalanced torque causes an angular acceleration. B. Torque has units of m N. C. Torque is proportional to the force applied. D. Torque is inversely proportional to the moment arm. 8. Which scientist did not hold to the heliocentric theory? A. Johannes Kepler B. Tycho Brahe C. Aristarchus of Samos D. Nicholaus Copernicus 9. Kepler s first law of planetary motion A. states that the position vector of a planet travels through equal areas in equal times if the vector is drawn from the Sun. B. relates the size of each planet s orbit to the time it takes to complete one orbit. C. states that the orbit of each planet is an ellipse with the Sun at one focus. D. states that the planets in each orbital system have their own K values. 10. The variable G that Cavendish calculated in Newton s law of gravitation is A. a universal constant. B. a very large quantity in SI units. C. an acceleration. D. a force. 11. Which is not true about Cavendish s experiment? A. He calculated G independent of the mass of the earth. B. He used torques to calculate G. C. He worked with objects of a small mass. D. He concluded his experiment with the calculation of G. Short Answer After reading each sentence, write a response in the blank provided. 12. The SI unit for angular measure is the. 13. The rate of change of angular speed with respect to time is called the. 14. The smooth motion of the second hand of a clock illustrates circular motion. 15. In circular motion, position vectors and velocity vectors are to one another. 16. The change in the angle of circular motion is analogous to the in linear motion. 17. The force that causes centripetal acceleration is the. 18. The quantity that causes accelerated rotation is called. 19. Ptolemy added the concept of epicycles to Aristotle s model to explain. 20. The law that states that a body travels around an ellipse at varying speeds depending on its distance from the Sun is Kepler s law.
Physics Test 7: Circular Motion page 3 21. The time it takes for one heavenly body to make one complete revolution around another heavenly body is called its. 22. The scientist who calculated the density of the earth was. 23. At the top of a loop of a roller coaster, the centripetal force is caused by. True/False Read the following statements. Identify each as true or false by putting T or F in the blank to the left. 24. Tangential acceleration is always perpendicular to centripetal acceleration. 25. The equation relating centripetal acceleration, tangential velocity, and the radius of motion is a vector equation. 26. Angular speed has the same magnitude but a different orientation than angular velocity. 27. Angular velocity and angular acceleration have different directions. 28. If the force applied is parallel to the position vector, then the torque is at a maximum. 29. For the most part, ancient philosophers and scientists held to the geocentric theory. 30. The closer a satellite is to the earth, the faster gravity spins the satellite around its orbit. 31. The Keplerian constant, K, is the same for Saturn s moon, Titan, as it is for all of our solar system s planets, asteroids, and comets. 32. The effects of gravity can be observed between two small masses. 33. If the magnitude of the tangential velocity on a merry-go-round is constant, then the centripetal acceleration vector must also be constant. 34. Calculations of the density of the earth led to a limited understanding of the earth s interior. Application Problems Complete the problems below. Be sure to show your work, consider significant figures, and put your answer with the correct units in the blank provided. 35. An automobile moves with a tangential speed of 45 m/s around a circular track with a 3200m diameter. What is the magnitude of the angular speed of the car?
Physics Test 7: Circular Motion page 4 36. A college student holds a pail full of water by the handle and whirls it around in a vertical circle at a constant speed. The radius of this circle is 0.95 m. What is the minimum speed that the pail must have at the top of its circular motion if the water is not to spill out of the upsidedown pail? 37. A ball having a mass of 0.60 kg is attached to the end of a cord 1.2 m long. The ball is swung in a circular path at the end of the cord with a speed of 6.0 m/s. What is the force in newtons which the string exerts on the ball? 38. What is the period of Io s orbit around Jupiter if the force of attraction is 4.90 10 21 N, the mass of Io is 6.88 10 21 kg, the mass of Jupiter is 1.90 10 27 kg, and the constant K = 3.21 10 15 m 3 /s 2 for the Jovian system?
Physics Test 7: Circular Motion page 5 39. Two spheres with masses of 5.00 g and 10.0 kg respectively are 0.500 m apart. Calculate the force of attraction between them. Essay Answer the following question in complete sentences. 40. How was the number for the density of the earth determined?