A fire man has to carry an injured person of mass 40 kg from the top of a building with the help of the rope which can withstand a load of 100 kg. The acceleration of the fireman if his mass is 80 kg, will be-

Two painters are working from a wooden hoard 5 m long suspended from the top of a building by two ropes attached to the ends of the plank. Either rope can withstand a maximum tension of 1040 N . Painter A of mass 80 kg is working at a distance of 1 m from one end. Painter B of mass 60 kg is working at a distance of x in from the centre of mass of the board on the other side. Take mass of the board as 20 kg and g = 10ms^(-2) . The range of x so that both the painters can work safely is

A boy of mass 20 kg , moved up to the top of a building of height 18 m , carrying a box of mass 2.5 kg. if he did this in 1.5 min, what was his rate of doing work ?

A man of mass 60 kg walks up to the top of a building of height 15 m. Calculate the increase in potential energy.

A man of mass 60kg lifts a 15 kg mass to the top of a building of height 10 m in 5 minutes. H is efficiency is