Q16 of 42 Page 33

A girl riding a bicycle along a straight road with a speed of 5 m s-1 throws a stone of mass 0.5 kg which has a speed of 15 m s-1 with respect to the ground along her direction of motion. The mass of the girl and bicycle is 50 kg. Does the speed of the bicycle change after the stone is thrown? What is the change in speed, if so?

Let m1 and m2 be the mass of girl with bicycle and stone respectively i.e. m1=50kg & m2=0.5kg

Also we have given u1=5m/s, u2=5m/s and v2=15 m/s and we have to find v1


As we know by law of conservation of momentum


initial momentum (girl, bicycle, stone) =final momentum (cycle and girl) + stone


i.e.






Therefore, the speed of cycle and girl decreased by



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