A race car is moving on a straight road with a speed of 180 kmh-1. If

1.	A race car is moving on a straight road with a speed of 180 kmh-1. If the driver stops the car in 25 s by applying the brakes, calculate the distance covered by the car during the time brakes are applied. Assume acceleration of the car is uniform throughout the retarding motion.
Answer» Initial speed μ = 180 kmh^-1 μ = 50 ms^-1 t = 25 s v = u – at v = 0 ∴ 0 = 50 – a × 25 ⇒ a = 2 ms^-2 v² = u² – 2as ⇒ s = μ²/2 a (50²/(2 x 2)) ∴ Stopping distance = 625 m

A race car is moving on a straight road with a speed of 180 kmh-1. If the driver stops the car in 25 s by applying the brakes, calculate the distance covered by the car during the time brakes are applied. Assume acceleration of the car is uniform throughout the retarding motion.

Answer»

Initial speed μ = 180 kmh^-1

μ = 50 ms^-1

t = 25 s

v = u – at

v = 0

∴ 0 = 50 – a × 25

⇒ a = 2 ms^-2

v² = u² – 2as

⇒ s = μ²/2 a

(50²/(2 x 2))

∴ Stopping distance = 625 m