Question

a porter with a suitcase on his head is climbing up step of flight with uniform speed work done by the weight of the suit case on the suit case is

Answer 1

The answer is 0. As the direction of dispacement is perpendicular to the direction of force! Force is downward while displacement of suitcase is forward so,
Work done = F*d*cos90 = 0, since cos90 = 0

Answer 2

positive as the man is applying upward force and the object is also moving upward