# The kinetic energy of the body is 7.5 J and its impulse is 5 kg m / s Find the mass and speed of the body

October 14, 2021 | education

| Given:

E = 7.5 Joules – kinetic energy of the body;

P = 5 kg * m / s – the value of the impulse of the body.

It is required to determine the body mass m (kilogram) and its speed v (meter per second).

Let m be the mass of the body, and its velocity v. Then:

E = m * v ^ 2/2.

P = m * v, hence: v = P / m.

Substitute the velocity value into the kinetic energy equation:

E = m * v ^ 2/2 = m * (P / m) ^ 2/2 = m * P ^ 2 / (2 * m ^ 2) = P ^ 2 / (2 * m), hence:

m = P ^ 2 / (2 * E) = 5 ^ 2 / (2 * 7.5) = 25/15 = 1.7 kilograms. Then:

v = P / m = 5 / 1.7 = 3 m / s.

Answer: body weight is 1.7 kilograms, body speed is 3 m / s.

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