# A stone weighing 100 g was thrown from the ground vertically upwards at a speed of 15 m / s.

A stone weighing 100 g was thrown from the ground vertically upwards at a speed of 15 m / s. Find the work of gravity acting on the stone when lifting the stone to its maximum height.

m = 100 g = 0.1 kg.

g = 9.8 m / s ^ 2.

V0 = 15 m / s.

V = 0 m / s.

A -?

The work of force A is determined by the formula: A = F * S * cosα, where F is the force, S is the displacement of the body under the action of the force, ∠α is the angle between force F and displacement S.

F = m * g.

S = h.

A = m * g * h * cosα.

The body moves vertically upwards, the force of gravity is directed vertically downwards, therefore ∠α = 180 “, cos180” = -1.

h = V0 ^ 2/2 * g.

A = – m * V0 ^ 2/2.

A = – 0.1 kg * (15 m / s) ^ 2/2 = – 11.25 J.

Answer: at maximum lift, gravity does the work A = – 11.25 J.

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