Fred swings a sheet of copper in pendulum fashion between the poles of a strong magnet. The sheet slows in entering the magnetic field because the field
A) induces swirling currents in the copper and accompanying magnetic fields that resist motion.
B) experiences both air and magnetic friction.
C) is repelled by free electrons in the copper.
D) none of the above
Answer: A
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Two masses are connected by a string which passes over a pulley with negligible mass and friction. One mass hangs vertically and one mass slides on a frictionless 30.0 degrees incline. The vertically hanging mass is 6.00 kg and the mass on the incline is 4.00 kg. The acceleration of the 4.00 kg mass is
A. 2.98 
B. 3.92
C. 5.88
D. 6.86
E. 7.84
How does an object’s rate of cooling vary with size?
a. A larger object cools more slowly than a smaller object. b. A smaller object cools more slowly than a larger object. c. Size has no effect on an object’s rate of cooling.
Which of the following studies is best suited to astronomical observations that fall into the category called timing?
A) studying how different planets differ in their surface compositions B) studying how a star's brightness varies over a period of 3 years C) measuring the rotation rate of a distant star D) determining the age of the solar system
A light source blinks with a certain frequency in its own frame of reference, and the speed of light in that frame is c. When the light source approaches you, you observe an increase in
A) both speed of light and frequency of blinking. B) speed of light, but not frequency of blinking. C) frequency of blinking, but not speed of light.