Answer:
To calculate the work done by John when lifting a 20kg mass to a height of 2m, we can use the formula: work = force x distance x cos(theta) where force is the weight of the mass (20kg x 9.81 m/s^2 = 196.2 N), distance is the height the mass is lifted (2m), and cos(theta) is the angle between the force and the displacement (cos(0) = 1, since the force and displacement are in the same direction). Substituting these values into the formula, we get: work = 196.2 N x 2m x 1 work = 392.4 J Therefore, John did 392.4 joules of work when lifting the 20kg mass to a height of 2m.