Question

A 150N force acts on a 300kg car calculate how long it takes this force to change the car velocity from 2m/s to 6m/s

Answer 1

We can find the time taken to change the car velocity from 2m/s to 6m/s from the definition of the impulse:

$$F \Delta t = \Delta p = m \Delta v,$$ $$F \Delta t = m(v_f - v_i),$$

here, $F$ is the force acting on the car, $\Delta t$ is the amount of time in which the force is acting (or the time taken to change the car velocity), $\Delta p$ is the impulse change, $m$ is the mass of the car, $\Delta v$ is the rate of change of car's velocity, $v_i$ is the initial velocity of the car and $v_f$ is the final velocity of the car.

From this equation we can find the time taken to change the car velocity:

$$\Delta t = \dfrac{m(v_f - v_i)}{F} = \dfrac{300kg \cdot (6 \dfrac{m}{s} - 2 \dfrac{m}{s})}{150N} = 8 s.$$

Answer:

$\Delta t = 8 s.$