Find the initial velocity of a body weighing 400 g if it, under the action of a force of 8 N

Find the initial velocity of a body weighing 400 g if it, under the action of a force of 8 N, reached a velocity of 6 m / s in 0.1 s.

When calculating, we will assume that the direction of application of the force coincides with the direction of the initial movement of the body.

Let us find the acceleration of the body, obtained under the action of the force. According to Newton’s second law:

F = m * a;

a = F / m = 8 / 0.4 = 20 m / s2;

The change in the speed of the body in 0.1 s under the action of the force will be:

Δv = a * t = 20 * 0.1 = 2 m / s2;

Let’s find the initial speed of the body:

v0 = v – Δv = 6 – 2 = 4 m / s.

Answer: v0 = 4 m / s.