A train rolls to a stop along a horizontal track without the conductor applying the brakes. What answer choice BEST explains why this occurred?
A) The train ran out of momentum.
B) The opposing force of friction stopped the train.
C) The natural state of the train is not to be in motion.
D) The force of gravity slowed the train until it stopped

A3.9 g aluminum foil ball with a charge of +4.1×10−9 c is suspended on a string in a uniform horizontal e⃗ field. the string deviates to the right and makes an angle of 30∘ with the vertical. part a part complete what information about the e⃗ field can you determine for this situation? what information about the field can you determine for this situation? only the magnitude of e⃗ only the direction of e⃗ both the magnitude and the direction of e⃗ none of the above previous answers correct part b determine the magnitude of the electric field. express your answer with the appropriate units. e e = nothing nothing request answer part c determine the direction of the electric field. determine the direction of the electric field. to the right to the left away from you toward you