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A strip of wood of length l is placed on a smooth horizontal surface. An insect starts from one end of the strip, walks with constant velocity and reaches the other end in time t1. It then flies off vertically. The strip moves a further distance l in time t2.(a) t2 = t1 (b) t2 < t1(c) t2 > t1(d) Either (b) or (c) depending on the masses of the insect and the strip |
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Answer» Correct answer is: (c) t2 > t1 The strip and insect will move in opposite directions such that their centre of mass is stationary. Their relative velocity is l/t1 and each will have speed < l/t1. When the insect flies off, the strip will continue to move at its previous speed and hence will cover a further distance l in time t2 > t1. |
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