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An object of mass 10 kg is made to fall freely from a height 20 m. Let us denote the starting point as A. The object strikes the ground with a velocity 'v' in 2 s. (Take g= 10 m/s2 in all parts )(i) Find the potential energy of the object after 0.5 s. |
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Answer» Answer mass, m = 1kg height, s = 20m initial velocity of ball, U = 0m/s acceleration, a = 10m/s 2
Using, v 2 = u 2 + 2as = 0 + 2×10 ×20 = 400 v = 20m/s Now, LET us take upward direction as POSITIVE and downward direction as negative. Initial momentum of the ball (before striking the ground) = m×v = 1×(-20) (velocity is downward, hence negative) = -20kgm/s Now, when the ball strikes and rebounds, its velocity becomes +20m/s (after striking, it moves upward, hence positive velocity) Final momentum (after striking the ground) = m×v = 1×(+20) = +20kgm/s Change in momentum = Final momentum - Initial momentum = 20kgm/s - (-20kgm/s) = 40kgm/s in upward direction. |
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