1.

A girl of mas 40 kg runs a height of 80 stairs, each 25 cm high witha load of of 20 kg on her head in 25s. If g is 10 m/s2Gravitational force acting on the girl.(11) Work done by her.(ii) Useful work done by the her.(iv) Her power in watt.​

Answer»

vitational force acting on the girl = Her mass in kg x g = 40 x 10 = 400 N(II) Total gravitational force = (Mass of girl + load) x g.= (40 + 20) x 10 = 600 N.and Distance or height = 80 x 25/100 = 20 m.∴ Work done by her = 600 N x distance∴ Total work done = 60 N x 20 m = 12000 J.(iii) USEFUL work done = Load x g x distance COVERED = 20 x 10 x 20 = 4000 J.(iv) POWER = Total work done/ Time= 12000/25W = 480 W.



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