posted by Joe .
You drop an egg from rest with no air resistance.
As it falls,
a. only its momentum is conserved.
b. only its kinetic energy is conserved.
c. both its momentum and its mechanical energy are conserved.
d. its mechanical energy is conserved, but its momentum is not conserved
There is a force on it in the direction of motion. Therefore its kinetic energy increases. However its total mechanical energy including the gravitational potential energy is conserved.
Meanwhile net force causes a rate of change of momentum, called acceleration when the mass is constant. Therefore the momentum changes.