Question

.Three boxes each weigh 100 N. A man lifts all the boxes together from the ground on to a shelf that is 1.5 m above the ground. The man takes 2.0 s to do this

Answer 1

Answer:

total weight of the boxes = 300 N

height =1.5 m

work done = 300 *1.5 = 450 J

power of man = 450/2 = 225 W

Answer 2

Answer:

Given that,

Weight of one box, W = 100 N

There are 3 boxes, total weight is 300 N

A an lifts all the boxes together from the ground on to a shelf that is 1.5 m above the ground.

The man takes 2.0 s to do this.

To find,

The useful power does the man produce to lift the boxes

Solution,

Power is given by the rate at which the work is done. It is given by :

$\begin{gathered}P=\dfrac{W}{t}\\\\P=\dfrac{mgh}{t}\\\\P=\dfrac{300\times 1.5}{2}\\\\P=225\ W\end{gathered}$

$P= </p><p>t</p><p>W</p><p> \\ </p><p> </p><p>P= </p><p>t</p><p>mgh</p><p> </p><p> \\ </p><p>P= </p><p>2</p><p>300×1.5$

$P=225 W$

So, the man will produce 225 W of power in lifting the boxes.