1.

The displacement of a body of mass `2 kg` veries with time `t` as `S = t^(2) + 2t`, where `S` is in seconds. The work done by all the forces acting on the body during the time interval `t = 2s` to `t = 4s` isA. `36 J`B. `64 J`C. `100 J`D. `120 J`

Answer» Correct Answer - B
`v = (dx)/(dt) = 2t + 2`
From work energy theorm,
` W_("net") = Delta K. E. = K_(f) - K_(i)`
`= (1)/(2) m (v_(f)^(2) - v_(i)^(2))`
`= (1)/(2) xx 2 [(2xx 4 + 2)^(2) - (2 xx 2 + 2)^(2)] = 64 J`


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