A cannon ball and a bowling ball were dropped at the same time from the top of a building. The cannon ball is more massive than the bowling ball. At the instant before the balls hit the sidewalk, the cannon ball had greater

Why is it so difficult to study the center of our galaxy? a. Light from the center is lost in the glow of emission nebulae in this direction

b. Interstellar dust blocks almost all light before it reaches Earth. c. The exact position of the center is not known. d. The center of the galaxy puts out very little radiation and is too dim to study. e. The center of the galaxy is too far away for radiation to be detected by telescopes.

Resistivity and Temperature: Over ordinary temperature ranges, the resistance of most metals such as copper

A. is independent of the temperature of the metal. B. decreases as the metal gets hotter. C. increases as the metal gets hotter. D. is a maximum at 20°C.

According to the law of reflection, the incident ray, reflected ray, and normal between them

A) lie in the same plane. B) may or may not lie in the same plane. C) lie in planes that are perpendicular to one another.

The mass number is equal to the number of what particles in the nucleus?

A) protons B) neutrons C) nucleons D) electrons E) positrons.