Question

An autodriver is driving with a speed of 36km/h. he applies the breaks and brings his vehicle to rest in 5 seconds. if the deceleration is 10 m/s^2 , calculate the distance travelled by the car before the breaks were applied​

Answer 1

Correct Question :-

An autodriver is driving with a speed of 36km/h. he applies the breaks and brings his vehicle to rest in 5 seconds. if the deceleration is 2 m/s² , calculate the distance travelled by the car after the breaks were applied

Given :-

◉ An autodriver is driving with initial speed of u = 36 km/h . He applies the breaks and brings his vehicle to rest in t = 5 seconds with a acceleration of a = -10m/s²

To Find :-

◉ Distance travelled by the car after the breaks were applied (A bit of mistake in your question)

Solution :-

First, Convert velocity into m/s

• u = 10 m/s
• a = -2 m/s²
• t = 5 s
• v = 0 m/s (Vehicle comes to rest)

Using second equation of motion,

⇒ s = ut + 1/2 at²

⇒ s = 10×5 + 1/2×-2×(5)²

⇒ s = 50 - 25

⇒ s = 25 m

Hence, The autodriver would travel 25 m after applying the break.

Some Information :-

Other equations of motion:

• 1st : v = u + at
• 2nd : s = ut + 1/2 at²
• 3rd : 2as = v² - u²

Why is your question incorrect?

If you really take, a = -10 m/s² and the initial velocity u = 10 m/s then the vehicle must be stopped after 1 s but It is given 5 seconds in the question.

So In order to stop the vehicle in 5 seconds, Acceleration should be -2 m/s².