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.