adiabatic process

Yes, a body with a velocity 0 can still accelerate. The simplest example is a body which is thrown up. At the peak point its velocity becomes 0 but still accelerates due to gravity. Hope it helps!!

At the first-year physics level — absolutely a normal force can do work. If an object moves parallel (or antiparallel) to a normal force, then the normal force has done work. The normal force is upward, movement is left, so the motion is not parallel to the normal force. No work is done by Fn.

In free expansion there is no work done as there is no external external pressure. That’s certainly true, in fact free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber, you can think of it like ann container with a piston and the gas is left to expand in vacuum.

The isothermal compression of the gas was performed in two ways, one irreversible and one reversible. The work done on the gas is positive because the gas is compressed; the surroundings do positive work on the gas. So the heat added to the compressed gas is negative, keeping the temperature constant.

The free expansion is an irreversible process. which describes an isothermal process, the path between the end points. The path between the end points is not defined for a free expansion. Bottom line: A free expansion in an insulated system is adiabatic, but it is not reversible adiabatic.

Adiabatic free expansion of a gas Because there is no external pressure for the gas to expand against, the work done by or on the system is zero. Since this process does not involve any heat transfer or work, the first law of thermodynamics then implies that the net internal energy change of the system is zero.