Question

What it the weight of an object that is held at a height of 4.5 m above the ground and has 300 j of energy?

Answer 1

The energy of an object held at a height of h is equal to its gravitational potential energy, given by
$U=mgh$
where m is the mass of the object, g is the gravitational acceleration and h is the height.

If we re-arrange the formula and we substitute the data of the problem, we can find the weight of the object, mg:
$mg= \frac{U}{h}= \frac{300 J}{4.5 m}=66.7 N$