A person applies a constant force of 20 N to a rock of mass 1000 kg, for a total of 20 seconds. What is the work done by this person if the rock does not move at all by this applied force?
A) 1000 J
B) 2000 J
C) 20,000 J
D) 0 J
E) 400 J
D
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A 25 nH inductor is in an AC circuit whose generator has an rms voltage of 12 V. At what frequency must the generator drive the circuit if the rms current is to be 2.0 mA?
A. 0.15 MHz B. 38 GHz C. 0.96 MHz D. 240 GHz
If Earth's mass were suddenly and magically reduced to half its present value, the magnitude of Earth's acceleration about the Sun would
A. be reduced by a factor of 4. B. be reduced by a factor of 2. C. remain the same. D. increase by a factor of 2.
How did Galileo know that the planets go around the sun rather than around Earth?
A) From telescopic observations of the phases of Venus as it moves around the sun. B) From telescopic measurements of the positions of the stars as Earth moved around the sun during the course of one year. C) From the writings of Aristarchus, the ancient Greek astronomer. D) By noting that Venus always lies near the sun, as seen from Earth, from which he concluded that Venus must be orbiting the sun. E) From measurements of the tides raised by the moon as compared with the tides raised by the sun.
Imagine that we place a spherical shell with a uniformly distributed positive charge Q and a particle with a negative charge -4Q as shown below. What are the directions of the total electric field vectors at the two points shown? 
What is the direction at point P1 at the shell’s center?
A. A B. B C. C D. D E. zero F. other G. AA H. BB I. CC J. DD