A boy's catapult is made of rubber cord which is long, with
diameter of cross-section and of negligible mass. The boy keeps a stone weighing
on it and stretches the cord by
by applying a constant force. When released, the stone flies off with a velocity of
. Neglect the change in the area of cross-section of the cord while stretched. The young's modulus of rubber is closest to :
For string
for stone
So apply energy conservation.
P.E. stored in string = K.E of stone
Option 4)
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