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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 work done by the porter in lowering the suitcase. (Take g=9.8 m s⁻²)

Asked in JEE Main 22nd July 2nd Shift 2021 · Work done by gravity and contact forces

• (1) -62720.0 J
• (2) +627.2 J
• (3) -627.2 J
• (4) 784.0 J

Step-by-step solution

Why the other options are wrong

• (1) Comes from leaving the 80 cm as 80 in the product.
• (2) Comes from getting the sign wrong; the porter's force is up while the displacement is down.
• (4) Comes from stopping at the force mg=784 N and never multiplying by the distance.

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