Answer :
Given data
*The given mass of the car is m = 900 kg
*The car is moving at a velocity is u = 20 m/s
*The given distance is s = 30 m
The formula for the acceleration of the car is given by the equation of motion as
[tex]\begin{gathered} v^2=u^2+2as \\ a=\frac{v^2-u^2}{2s} \end{gathered}[/tex]*Here v = 0 m/s is the final velocity of the car
Substitute the known values in the above expression as
[tex]\begin{gathered} a=\frac{(0)^2-(20)^2}{2\times30} \\ =-6.67m/s^2 \end{gathered}[/tex]The formula for the frictional force is required to stop it at a distance of 30 m is given as
[tex]f=ma[/tex]Substitute the known values in the above expression as
[tex]\begin{gathered} f=(900)(-6.67) \\ =-6000\text{ N} \end{gathered}[/tex]Hence, the frictional force is required to stop it at a distance of 30 m is f = -6000 N