Answer
$F=6800N$
Work Step by Step
First, convert the speed to meters per second. Perform dimensional analysis to get a speed of $$\frac{53km}{1hr} \times \frac{1hr}{60min} \times \frac{1min}{60s} \times \frac{1000m}{1km}$$ $$=14.7m/s$$ To find the force, you must know the acceleration. To find acceleration, use a kinematics equation relating acceleration, initial velocity, final velocity, and displacement. This is $$v_f^2=v_o^2+2a\Delta x$$ Solving for $a$ yields $$a=\frac{v_f^2-v_o^2}{2\Delta x}$$ Substituting known values of $v_f=0.0m/s$, $v_o=14.7m/s$ and $\Delta x=0.65m$ yields an acceleration of $$a=\frac{-(14.7m/s)^2}{2(0.65m)}=-166m/s^2$$ Using Newton's second law $F=ma$ and a known value of $a=166m/s^2$ and $m=41kg$ yields a force of $$F=(166m/s^2)(41kg)=6800N$$
