I need to finish this lesson and i have a large test tomorrow. Please help! Under what circumstances can the general trend to disorder in the universe be reversed?

What is the coefficient of kinetic friction μk between the block and the tabletop?

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.

Blank is the perceived frequency of a sound wave