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3.a) A metal ball of mass 60 g falls on a concrete floor from a vertical height of 2.8m and rebounds to a height of 1.3 m. Find the change in P.E. |
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Answer» -Mass of ball = m = 60 g = 0.06 KGACCELERATION due to GRAVITY = g = 10 ms-²Height COMING down = H = 2.8 m Height rebounds = h = 1.3 m While coming down Potential Energy,P.E. = mghP.E. = 0.06(10)(2.8)P.E. = 1.68 J Again while rebounds,Here, Acceleration will act in opposite direction of motion,g = -10 ms-²P.E.' = mghP.E.' = 0.06(-10)(1.3)P.E.' = -0.78 JNegative Sign INDICATES that Potential Energy is acting in opposite direction.∆P.E. = P.E. - P.E.'∆P.E. = 1.68 - (-0.78) ∆P.E. = 2.46 J |
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