Question

What forces are acting on a block

Answer 1

if it is moving on a horizontal plane (or) inclined plane, the forces acting on the block are Normal Reaction(perpendicular to the surface of plane),
External Force(in the direction of motion)..if applied,
Frictional Force(in the direction opposite to applied force),
Weight of the block(acting downwards).

if the block is tied with the help of a string, Tension acts upwards(towards the point of suspension of rope)

if the block is moving on a curved path, Centrifugal Force also acts(away from the centre)

hope this helps you...cheers!!