Assertion: If a body is thrown upwards,the di | vedclass

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Question

(A) For the upward motion,the final velocity at the highest point is $v = 0$. Using the equation of motion $v = u + at$,for the last second of motion,

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If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

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(A) For the upward motion,the final velocity at the highest point is $v = 0$. Using the equation of motion $v = u + at$,for the last second of motion,the initial velocity $u'$ at the start of that last second is $u' = v - at = 0 - (-g)(1) = g$. The distance covered in the last second is $s = u't + \frac{1}{2}at^2 = g(1) + \frac{1}{2}(-g)(1)^2 = g - \frac{g}{2} = \frac{g}{2}$. Taking $g \approx 10 \ m/s^2$,we get $s = \frac{10}{2} = 5 \ m$. This distance is independent of the initial velocity of projection. The reason is also correct because the motion is symmetric; the distance covered in the last second of upward motion is identical to the distance covered in the first second of free fall (downward motion) starting from rest $(u=0)$. Thus,both Assertion and Reason are correct,and the Reason explains the Assertion.

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