Question

A box is lifted to a height of 6 meters in 3 seconds. If the lift required 400 watts of power, what was the weight of the box?200 N250 N300 N350 N

Answer 1

Given:

The height through which the box was lifted, h=6 m

The time it took to lift the box, t=3 s

The power dissipated in lifting the box, P=400 W

To find:

The weight of the box.

Explanation:

The power is described as the time rate of transfer of energy.

Thus the power is given by,

$P=\frac{W}{t}$

Where W is the work done in lifting the box.

The work done is given by,

$W=F\times h$

Where F is the weight of the box.

Thus the power dissipated in lifting the box is given by,

$P=\frac{Fh}{t}$

On substituting the known values,

$\begin{gathered} 400=\frac{F\times6}{3} \\ \Rightarrow F=\frac{400\times3}{6} \\ =200\text{ N} \end{gathered}$

Final answer:

The weight of the box is 200 N

Thus the correct answer is option A.