A 5 kg bag is lifted slowly from the ground to a height of 2 m. Taking g = 10 m/s², the work done against gravity is:

Lifting at constant velocity means the applied force balances gravity = mg = 5 × 10 = 50 N. Work done = force × height = 50 × 2 = 100 J. This work is stored as gravitational potential energy in the bag (PE = mgh = 5 × 10 × 2 = 100 J).