Answer
(a) $18.7KN$
(b) Please see the work below.
Work Step by Step
(a) We can find the required force as follows:
$a=\frac{v^2-v_{\circ}^2}{2\Delta x}$
We plug in the known values to obtain:
$a=\frac{[(45.0mi/h)^2-(202mi/h)^2](\frac{0.447m/s}{mi/h})^2}{2(185)}$
$a=-20.94m/s^2$
Now $\vec F=m\vec a$
We plug in the known values to obtain:
$\vec F=(89Kg)(-20.94m/s^2 \hat x)=(-18700N)\hat x=(-18.7KN)\hat x$
(b) We determine the required force by calculating the acceleration from the speeds and displacement given. We use the second law of motion and plug in the known values to obtain the required force.
