Sound waves
a. have an irregular vibration pattern.
b. do not require a medium for transmission.
c. are a change of pressure that moves through matter.
d. move at the same rate at any given temperature.

While carrying a heavy box up the stairs,you set the box on a step and rest. then you pick up the box and carry it to the top of the stairs. describe these actions in terms of balanced and unbalanced forces acting on the box.