Question

A rock weighing 98 newtons is pushed off the edge of a bridge 50 meters above the ground. What was the potential energy of the rock before it began to fall?

Answer 1

Answer: The potential energy of the rock before it began to fall is 4900 J

Explanation:

Force is defined as the mass multiplied by the acceleration of the object.

$F=mg$

where,

F = force exerted on the object

m = mass of the object

g = acceleration due to gravity

Potential energy is defined as the energy possessed due to the height of the object.

Mathematically,

$E_p=mgh$

Or,

$E_p=F\times h$

where,

$E_p$ = potential energy of the rock = ?

F = force applied on the rock = 98 N

h = height of the bridge from where the rock is thrown = 50 m

Putting values in above equation, we get:

$E_p=98N\times 50m\\\\E_p=4900J$

Hence, the potential energy of the rock before it began to fall is 4900 J

Answer 2

Ep = 4900 because Ep = wh