IF there is no friction against the moving object (impossible in real life),
then it takes NO force to keep the object moving at a constant speed
in a straight line.
It takes force only to CHANGE the object's motion ... speed it up, slow
it down, or change its direction.
Kinetic energy is simply 1/2 *mass* velocity^2
so since you know both mass and velocity you should be able to calculate the kinetic energy.
I just need points to ask my own question.
The man is holding the suitcase at the same height above the surface of earth. So the gravitation potential energy remains the same.
<span>work done is force * displacement = weight * 0 = 0</span>
