When a body is moved with uniform velocity/speed, how the work is defined because here acceleration is 0 . It means force is 0.So, work done should also be 0 but actually its not ?

There is actually no work done if there is 'no force' acting on the body, or if the 'velocity' does not change. But in case of a non conservative force like friction, if you are keeping the velocity of body constant, then definitely you have to work against the dissipative forces of friction. You can see this by Work Energy theorem also. WE theorem tells, W(c)+W(nc)+W(ext)= change in Kinetic energy. since W done by conservative force zero and change in kinetic energy is also zero, hence W done by external agent = work done by non conservative forces with a -ve direction.

Thank you

work done = force x displacement

in case of constant velocity

1- work done will be zero, if constant velocity is maintained without any external force like any object is moving on smooth surface.

2 - work done will not be zero, if any external force is applied to maintain the constant velocity, like object on a rough surface. In this case work is done against friction forces.