Which of the following objects exerts a gravitational force? a. the Sun b. an apple c. a basketball d. the Earth e. the Moon

Electrons are modeled using a "cloud" around the nucleus because they A) can not be precisely located. B) travel at the speed of light. C) exist in many places at once. D) move in an orbit about the nucleus.

How would local winds be affected if water and land release heat at the same time

Why is the true surface of a perfect mirror invisible?

A man wishes to pull a crate 15m across a rough floor by exerting a force of 100 N. The coefficient of kinetic friction is 0.25. For the man to do the least work, the angle between the force and the horizontal should be: A. 0 B. 14? C. 43? D. 66? E.

Ball A is negatively charged and ball B is electrically neutral. What happens to the charges of both balls when they come into contact with each other if: a) they are made of an electrical conductor b) they are made of insulator

Which of Newton's laws, when combined algebraically with his law of universal gravitation, can be used to calculate Earth's mass? A) first B) second C) third

Why does a balloon filled with helium rise while a balloon filled with an equal volume of average atmospheric air does not? A. Helium has no mass, but air does. B. Helium increases the balloon's mass more than air. C.

Consider the following controls in an automobile in motion : gas pedal, brake, steering wheel. what are the controls in this list that cause an acceleration of the car?

What material are oil pipelines made from?

3/129 A 175-lb pole vaulter carrying a uniform 16-ft, 10-lb pole approaches the jump with a velocity v and manages to barely clear the bar set at a height of 18 ft. As he clears the bar, his velocity and that of the pole are essentially zero.