The point moves in a straight line according to the law x (t) = 5t ^ 3 + 3 Find the speed of movement at t = 4

We have been given a move function. We take the derivative from it and obtain the velocity function (the physical meaning of the derivative):
v (t) = x ‘(t) = (5 * t³ + 3)’ = 5 * 3 * t² + 0 = 15 * t².

Let’s find the speed at the moment of time t0 = 4:
v (t0) = 15 * 4² = 15 * 16 = 240 m / s.

Answer: the instantaneous speed of movement of a point at time t0 = 4 s is 240 m / s.