A 4 kg rock is at the edge of a cliff 30 meters above a lake. It becomes loose and falls toward the water below.
Calculate its potential and kinetic energy when it is at the top and when it is halfway down.
Its speed is 16 m/s at the halfway point. pls answer

Which sentence about particles in matter is true? a. atoms are present in solids and liquids but not in gases. b. the particles of matter are in constant motion. c. the same kinds of atoms are found in different elements. d. when a solid changes to a liquid, the sizes of the particles change.