I am stuck thinking about work done by non-conservative forces. It is path dependent.
Let us consider an example.
A truck starts from rest and a block is kept on it. It accelerates for some time and then the driver applies brakes and the truck stops. In all this process, the block is moving with the truck. So what is the work done by the friction on the block?
Is it force time displacement ? Or is it zero as the change in kinetic energy over this time period is zero?