What is the mass of a body that fell from a height of 20 m to the ground, if the work of gravity was 3920 J.

Initial data: h (height from which the considered body fell) = 20 m; A (value of the work of gravity) = 3920 J; the body fell vertically downward (cosα = 1).

Reference values: g (acceleration due to gravity) = 9.8 m / s2.

The mass of the body is determined from the formula for calculating the work: A = F * S * cosα = m * g * h, whence m = A / (g * h).

Let’s calculate: m = 3920 / (9.8 * 20) = 20 kg.

Answer: The weight of the fallen body is 20 kilograms.