Conceptual question about relativity: imagine two events--
1. a photon hits a mirror
2. the same photon, after reflecting off of the mirror, hits some other surface.

these two events are separated in both space and time. however, the spacetime separation between the two events is zero.

what does this mean? normally if the distance between two points is zero, it means that the two points are identical. are these two events, in some sense, the same event?

According to newton's second law, when the same force is applied to two objects of different masses, a the object with greater mass will experience a great acceleration, and the object with less mass will experience an even greater acceleration, b. the object with greater mass will experience a smaller acceleration, and the object with less mass will experience a greater acceleration, c. the object with greater mass will experience a greater acceleration, and the object with less mass will experience a smaller acceleration, d. the object with greater mass will experience a small acceleration, and the object with less mass will experience an even smaller acceleration.

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

Carbon-14 is a radioactive element that undergoes beta decay. which force is responsible for allowing carbon-14 to become stable? electromagnetic gravitational weak nuclear strong nuclear