To calculate the retardation produced in the car, you can use the following formula:
retardation (a) = (final velocity squared - initial velocity squared) / (2 * distance)
In this case, the initial velocity (u) of the car is 18 km/h, which needs to be converted to m/s:
18 km/h = 18 * (1000 m / 3600 s) = 5 m/s (approximately)
The final velocity (v) of the car is 0 m/s since it comes to rest.
The distance traveled (s) is given as 5 m.
Now, substitute these values into the formula:
retardation (a) = (0^2 - 5^2) / (2 * 5) = (-25) / 10 = -2.5 m/s²
The negative sign indicates that the retardation acts in the opposite direction to the initial motion of the car, which is expected when the brakes are applied.
Therefore, the retardation produced in the car is approximately -2.5 m/s².