Solution:
Given,
Mass of an object (m) = 3 kg,
height = distance covered by stone (h) = 3 m,
Acceleration due to gravity (g) = 10 m/s2
Work done against the gravity = force (F) × displacement (h) = F × h
We also know that Force (F) = Mass of an object (m) × acceleration due to the gravity (g) = m×g
Hence, the work done against gravity becomes
W = m×g×h
= 3 kg × 10 m/s2 × 3m
= 90 joule
Hence, the work done against gravity is 90 Joule.