JEE Mains · Physics · STD 11 - 5. work,energy,power and collision
A porter lifts a heavy suitcase of mass \(80\, {kg}\) and at the destination lowers it down by a distance of \(80\, {cm}\) with a constant velocity. Calculate the workdone by the porter in lowering the suitcase. (take \(g=9.8\, {ms}^{-2}\) ) (In \({J}\))
- A \(+627.2 {J}\)
- B \(-62720.0 {J}\)
- C \(784.0 {J}\)
- D \(-627.2 {J}\)
Answer & Solution
Correct Answer
(D) \(-627.2 {J}\)
Step-by-step Solution
Detailed explanation
\(W_{\text {Porter }}+W_{m g}=\Delta K . E_{.}=0\) \(W_{\text {Porter }}=-W_{{mg}}=-m g h\) \(=-80 \times 9.8 \times 0.8=-627.2\, {J}\)
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