Work is done when force is applied a for a long enough period of time.
b in the opposite direction that the object moves.
c in the same direction that the object moves.
d two of the above

What is the weight of a feather (mass = 0.0001 kg) that floats through earth's and the moon's atmospheres?

The energy equivalent of the rest mass of an electron is

Ahair dryer is basically a duct in which a few layers of electric resistors are placed. a small fan pulls the air in and forces it through the resistors where it is heated. air enters a 1200 w hair dryer at 100 kpa and 22°c and leaves at 47°c. the cross-sectional area of the hair dryer at the exit is 60 cm2. neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine (a) the volume flow rate of air at the inlet and (b) the velocity of the air at the exit.