# 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?

Jul 1, 2018

$\text{75 J}$

#### Explanation:

• Displacement $= \setminus \text{3 m}$
• Mass $= \setminus \text{2.5 kg}$

$\textcolor{red}{\text{Force" = "mass" xx "acceleration}}$

The acceleration due to gravity $= {\text{10 m/s}}^{2}$ (approx)

So

$\text{Force" = "2.5 kg" xx "10 m/s"^2 = "25 N}$

Now use

$\text{Work}$ $\text{done" = "force" xx "displacement} \times \cos \theta$

Here

$\theta = {0}^{\circ} \implies \cos \left(\theta\right) = 1$

So

$\text{work" = "25 N" xx "3.0 m" xx 1 = "75 J}$