Parallel Wires: An object is hung using a metal spring. If now a current is passed through the spring, what will happen to this system?
A. The spring will contract, raising the weight.
B. The spring will extend, lowering the weight.
C. The weight will not move.
D. The spring will begin to swing like a pendulum.
E. None of these are true.
Answer: A
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Why are collisions between galaxies common, but collisions between stars rare?
A) Stars are very small compared to the distances between them, but galaxies are not. B) Stars repel each other with stellar winds, but galaxies do not. C) Stars are much less common than galaxies, so there are fewer of them to collide. D) Stars do not survive as long as galaxies, so they have less time to collide.
A distance R away from a light source we observe which of the following for the electromagnetic field it produces?
A) Both the light intensity and the magnitude of the electric field drop as 1/R2. B) The light intensity drops as 1/R2, but the magnitude of the electric field drops as 1/R. C) Both the light intensity and the magnitude of the electric field drop as 1/R. D) The light intensity drops as 1/R, but the magnitude of the electric field drops as 1/R2. E) None of the previous answers is correct.
A mass is attached to a vertical spring and bobs up and down between points A and B. Where is the mass located when its kinetic energy is a minimum?
A) at either A or B B) midway between A and B C) one-third of the way between A and B D) one-fourth of the way between A and B E) none of the above
Why are Earth and other planets spherical while smaller bodies such as most asteroids are not?
A. The larger mass of a planet produces enough gravity to pull it into a round shape. B. It is the nature of massive objects to pull themselves into spherical shapes. C. Asteroids were never molten, and so never underwent differentiation. D. Earth and other planets formed from planetesimals pulled together by gravity into circular orbits. E. The atmosphere of a planet is heavy enough to push the planet into a round shape.