# A stone thrown from the Earth’s surface at a speed of 10 m / s had a kinetic energy of 5 J

May 27, 2021 | education

| **A stone thrown from the Earth’s surface at a speed of 10 m / s had a kinetic energy of 5 J at the top point of the trajectory. Determine the mass of the stone.**

The mass of a stone can be expressed from the following formula:

Ek = m * V² / 2, where Ek is the kinetic energy of the thrown stone (Ek = 5 J), m is the required mass of the stone (kg), V is the speed of the stone (V = 10 m / s).

m = 2Ek / V².

Let’s make a calculation:

m = 2Ek / V² = 2 * 5/102 = 10/100 = 0.1 kg.

Answer: The weight of the thrown stone is 0.1 kg or 100 g.

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