Question

A car traveling with a velocity of 40m/s. The driver applied brakes with a uniform retardation.
Find the time required to bring the car at rest
Calculate the distance travelled by the car after applying brake

Answer 1

Answer:

The car moving with an initial velocity of 40 m/s, stops after a displacement of 120m on application of brakes. We are required to find the car's deceleration and the time taken to stop the car.

Initial velocity (u) of the car = 40 m/s

Final velocity of the car (v) = 0 m/s

Displacement of car before stopping (s) = 120 m.

Using the relation: v² - u² = 2 a s

0² - 40² = 2× a × 120; ==> a = - 40²/(2×120) =-(20/3) m/s²

The acceleration of the car =-20/3 m/s² = - 6.666 m/s² ( negative sign signifies deceleration).

We can find time taken using: v = u + a t

So time t taken to stop the car.

0 = 40 - (20/3)× t ; ==> t = 40×3/20 =6 s.

The car stops in 6 second after the brakes are applied and kept applied.