Question

A hat weighing `5"N"` is placed on a hook `1.5"m"` above the ground. What is the potential energy of the hat?

Answer 1

`U_g=7.5J`

Explanation:

Gravitational potential energy is given as

`U_g=mgh`

where `m` is the mass of the object, `h` is the object's height above the ground (surface of the earth), and `g` is the free-fall acceleration constant, `9.8m/s^2`.

We're given the weight of the hat, however, not the mass. The weight of a stationary object is given as the force of gravity acting upon it, which is the product of its mass and `g`.

`W=vecF_g=mg`

So, `mg=5N` and `h=1.5m`

`=>U_g=(5N)(1.5m)=7.5Nm=7.5J`