Question

A rock with a mass of 2.0 kg falls from a cliff. At a height of 5.0 meters, its velocity is 6.0 m/s. What is the mechanical energy of the rock?

Answer 1

The mechanical energy of the rock is 134.0665 J.

Answer 2

Answer : The mechanical energy of the rock is, 134 J

Solution :

As we know that the mechanical energy is equal to the sum of the kinetic energy and the potential energy.

The formula used for mechanical energy is,

`M.E=K.E+P.E\\\\M.E=((1)/(2)mv^2)+(mgh)`

where,

M.E = mechanical energy

K.E = kinetic energy

P.E = potential energy

m = mass of an object = 2 Kg

v = velocity of an object = 6 m/s

h = height = 5 m

g = acceleration due to gravity =
`9.8m/s^2`

Now put all the given values in the above formula, we get the mechanical energy of the rock.

`M.E=[(1)/(2)(2Kg)* (6m/s)^2]+(2Kg* 9.8m/s^2* 5m)=134\text{ Kg }m^2s^(-2)=134J`

Therefore, the mechanical energy of the rock is, 134 J