Answer: 6 Joules
Explanation:
You are given that the potential energy P.E of the apple = 18 Joules
PE = mgh
Where g = 9.8 m/s^2
18 = mgh
Initially, The mechanical energy of the apple = 18 Joule.
According to conservative of energy
the total energy of the apple will be 18 Joules. That is,
K.E + P.E = 18 Joules
when the apple has fallen to one third its original height, the remaining height from the ground upward will be:
height h = 1 - 1/3 = 2/3
The new Potential energy will be
P.E = 2/3 × 18
P.E = 12 Joules
The potential energy lost must have been converted to the kinetic energy according to conservative of energy
K.E + 12 = 18
Make K.E the subject of formula
K.E = 18 - 12 = 6 Joules
Therefore, the apple will have 6 Joules of kinetic energy when it has fallen to one third its original height.
