When introduced into a region where an electric field is present, a proton with initial velocity 
will eventually move
A. along an electric field line, in the positive direction of the line.
B. along an electric field line, in the negative direction of the line.
C. to a point of decreased potential.
D. to a point of decreased potential.
E. as described in both (a) and (c).
Answer: C
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Consider again the civilization described in the previous question. (They live on a planet orbiting 10 AU from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole surrounded by an accretion disk
) One foolhardy day, a daring individual in their space force (let's call him Major Tom) decides to become the first of his species to cross the event horizon of the black hole. To add to the drama, he decides to go in wearing only a thin space suit, which offers no shielding against radiation, no cushioning against any forces, and so on. Which of the following is most likely to kill him first (or at least to start the process of killing him first)? A) tidal forces due to the black hole B) the crush of gravity at the singularity embedded within the black hole C) X-rays from the accretion disk D) the sucking force from the black hole, which will cause his head to explode
You have a set of 14 metal weights strung together by nylon fishing line at equal intervals. Each has a weight of 0.20 N. You suspend this array from the ceiling and then observe waves travel up and down by shaking it.
The wave seems to move more rapidly at the top, near weights 1-3. This is because
A. gravity is cancelled by tension, so net force is zero. B. there is more tension in the fishing line near weights 1-3 than down by weight 14. C. weight 14 is balanced by no other weight, but weight 1 is balance by 13 others below it. D. the amount of mass per centimeter is higher toward the top, near weights 1-3.
When electric current is flowing in a metal, the electrons are moving
A) at nearly the speed of light. B) at the speed of light. C) at the speed of sound in the metal. D) at the speed of sound in air. E) at none of the above speeds.
Suppose you left five 100-W light bulbs burning in the basement for two weeks. If electricity costs 10.0¢/kW?h,
(a) how much did the electricity cost (to the nearest dollar) to leave those bulbs on, and (b) how many joules of electrical energy did they consume?