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13) A girl having amass of 50 kg sits on a trolley of mass 10 kg. The trolley is given an initial velocityof 5 m/sec by applying a force. The trolley comes to rest after traversing a distance of 12.5 metre.a) How much work is done by the girl?b) How much work is done on the trolley?

Answer»

mass of girl = 50kg

mass of trolley = 10kg

Total mass,m= (50+10) = 60 kg

u =5m/s,v= 0,s= 12.5 m.

Using kinematics equation,v2=u2+ 2as

⇒ 0 = (5)2+ 2a(12.5)

⇒ 25a= –25

⇒a= –1m/s2

Force exerted on trolley, F =ma= 60×1 = 60N

(a) Work done on trolley W = FS = (60N) (12.5 m) = 750J

(b) Work done by the girl, W = FS

= (mass of girl) × retardation × S

= 50 × 1 × 12.5

= 625 J

thank you



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