Which of the following options contain systems that possess both kinetic energy and potential energy?
1. A boy standing on the top of a building.
2. A descending airplane moving with a velocity v.
3. A book placed on the table.
4. An apple on a tree.

50 g of ice at 0°c is dropped in a beaker containing 100 g of water at 0°c. what will be the contents of the beaker after 5 hours? assume that the room temperature is 0°c.

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.

Apulley with mass mp and a radius rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot.