At the point of contact, work done by the normal reaction when a person climbs up the stairs is
It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B of same mass does the same in 15 s.Compare the (i) work done, and (ii) power developed by the persons A and B.
A boy of mass m climbs up the stairs of vertical height h.
(a) What is the work done by the boy against the force of gravity?
(b) What would have been the work done if he uses a lift in climbing the same vertical height?
State whether work is done or not by writing yes or no, in the following cases:
(a) A man pushes a wall.
(b) A coolie stands with a box on his head for 15 min.
(c) A boy climbs up 20 stairs.
A boy of mass 40kg climbs up the stairs and reaches the roof at a height 8m in 5s.Calculate :
1-the force of gravity acting on the boy
2-the work done by him against the gravity
3-the power sent by the boy
(take g=10m 1/s²)