A box of mass 2.5 kg is lifted from the floor to a shelf 3.0 metres above the floor. How much work is done?

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Answer 1 · 2018-07-01T10:44:19

$"75 J"$

$color(red)("Force" = "mass" xx "acceleration")$

The acceleration due to gravity $= "10 m/s"^2$ (approx)

So

$"Force" = "2.5 kg" xx "10 m/s"^2 = "25 N"$

Now use

$"Work"$ $"done" = "force" xx "displacement" xx cos theta$

Here

$theta = 0^@ => cos(theta) = 1$

So

$"work" = "25 N" xx "3.0 m" xx 1 = "75 J"$