A stone weighing 1 kg was thrown vertically upward with an initial speed of 8 ms, when the speed

A stone weighing 1 kg was thrown vertically upward with an initial speed of 8 ms, when the speed decreased to 2 m / s, the force of gravity did the job.

To find the height at which the stone will be, use the formula:
h = (v0 ^ 2 – v ^ 2) / 2g, where g is the acceleration of gravity, v0 is the initial velocity, v is the velocity at the specified height. Substituting the values from the condition of the problem into the formula, we get:
h = (8 ^ 2 – 2 ^ 2) / 2 * 10 = 3 m.
The work of gravity will be equal to the potential energy of the stone at this height:
A = W = m * g * h.
We supply quantities:
A = 1 * 10 * 3 = 30 J.
Answer: the required work is 30 J.