When the stone was at a height of 20 m, it had only potential energy. In the process of falling, potential energy passed into kinetic energy. At the moment the stone hits the ground, all potential energy has passed into kinetic energy.
It turns out that:
Ekin = Bp.
It is known from the physics course that the potential energy is equal to:
Ep = m * g * h, where h is height, m is body mass, g = 9.8 m / s ^ 2.
Let’s substitute the obtained values:
Ep = 50 kg * 20 m * 9.8 m / s ^ 2 = 9800 J or 9.8 kJ rounded to 1000 J.
Answer: the kinetic energy was 1000 J.
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