Question

You did $150joules$ of work by lifting a $120Newton$ backpack.

a) How high did you lift the backpack?
b) How much did the backpack weigh in pounds?

Answer 1

(a) Work done is equal to the change in potential energy of the backpack

Hence, $W=mgh$

where, weight of object $=mg$, and $h$ is the height to which the backpack is lifted

Hence,

$150=120\times h$

$h=\frac{150}{120}=\frac{5}{4}=1.25m$

(b) Since, $1pound=4.448N$

Let $120N=x$ pounds

$=x\times 4.448N$

$x=\frac{120}{4.448}=26.98$

Hence $120N=26.98pounds$