To find the acceleration of the car, we can use the following relationship:
[tex]v_f^2 - v_i^2 = 2 aS[/tex]
where
[tex]v_f=0[/tex] is the final speed of the car (it is zero because the car comes to rest)
[tex]v_i=20 m/s[/tex] is the initial speed of the car
[tex]a[/tex] is the acceleration
[tex]S=20 m[/tex] is the distance covered
By rearranging the equation, we get:
[tex]a= \frac{-v_i^2}{2 S}= \frac{-(20 m/s)^2}{2 (20 m)} =-10 m/s^2 [/tex]
where the negative sign means it is a deceleration.
