Answer:
electrons can be knocked loose from one object and picked up by the other. The object that gains electrons becomes negatively charged, while the object that loses electrons becomes positively charged.
The second, fourth, and seventh answers apply. Energy in a closed system is conserved, but it can change form
Definition: Frequency is the measurement of the number of times that a repeated event occurs per unit of time. Sound moves through a medium such as air or water as waves. It is measured in terms of frequency and amplitude. Frequency, sometimes referred to as pitch, is the number of times per second that a sound pressure wave repeats itself.
