Solution:
Here, the vertical height of the inclined plane (h) = 3m,
Mass of the kid (m) = 40 kg,
Acceleration due to gravity (g) = 9.8 m/s^2
We know, the potential energy (PE) of an object = mgh
= 40 × 9.8 × 3
= 1176 Joules
Hence, the potential energy of the kid is 1176 J or 1.176 KJ (kilojoules)