PHYSICS 1403, QUIZ 3
Chapter 5
March 1, 2004
Partial credit will be LIBERAL, provided that you show your work!
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1. (10 points) CONCEPTUAL QUESTION. See figure. A ball, mass m, is twirled at the
end of a string in a vertical circle of radius r at constant speed v. Free body diagrams for
the ball at the top and at the bottom of the circle are shown. Is the string tension FTA that
the string exerts on the ball at the top of the circle (point A) less than, more than, or the
same as the tension FTB at the bottom of the circle (point B)? Why? Explain your answer
using Newton’s 2nd Law with centripetal acceleration!
2. (20 points). See figure. A satellite of mass m = 1500 kg is in a circular orbit at constant speed around planet X, which is assumed to be a uniform sphere. (The resemblance to Earth is coincidental!) The radius of the orbit (measured from the planet’s center) is r = 6 ´ 107 m. The planet’s mass is M = 8 ´ 1024 kg. The gravitational constant is G = 6.67 ´ 10-11 N m2/kg2.
a. Compute the gravitational force of attraction between the satellite and the planet.
b. Compute the centripetal acceleration experienced by the satellite. What is the direction of this acceleration? (Hint: You don’t need to know the speed of the satellite to answer this! Use the results of part a. along with Newton’s 2nd Law).
c. Use the results of part b. to compute the speed of the satellite in orbit.
d. What is the period of this satellite’s orbit?