Question

A race car with a mass of 1500 kg travels at a speed of 6.7 m/s down a track. Compute the time required for a force of 1500 N to bring the car to rest.

Answer 1

ANSWER

$6.7s$

EXPLANATION

We want to find the time required for the force to bring the car to rest.

To do this, we have to apply the relationship between the change in momentum and force:

$\Delta p=F\cdot t$

where t = time

Simplifying this, we have that the time required is:

$\begin{gathered} m(v_2-v_1)=F\cdot t \\ \Rightarrow t=\frac{m(v_2-v_1)}{F} \end{gathered}$

where v1 = initial velocty = 6/7 m/s

v2 = final velocity = 0 m/s

Since the force is bringing the car to a rest, it is a repulsive force, hence, it is negative.

Therefore, the time required is:

$\begin{gathered} t=\frac{1500(0-6.7)}{-1500} \\ t=\frac{1500\cdot-6.7}{-1500} \\ t=6.7s \end{gathered}$

That is the answer.