Question

A bus is traveling at 72km/hr. Brakes are applied and the bus comes to astop after10m. Find the rataradratiin of the brakes.

Answer 1

Given :

• Initial velocity of Bus, u = 72 km/h
• Final velocity of Bus, v = 0  

 [ Since, Bus will come to rest ]

• Distance covered by Bus after applying brakes, s = 10 m

To find :

• Retardation produced due to Brakes

Formula required :

• Third equation of motion

      2 a s = v² - u²

[ Where a is acceleration, s is distance covered, v is final velocity and u is initial velocity of body ]

Solution :

Converting initial velocity of Bus given in km/h to m/s

→ u = 72 km/h

→ u = 72 × 5 / 18

→ u = 20 m/s

Calculating acceleration of the Bus

→ 2 a s = v² - u²

→ 2 a ( 10 ) = ( 0 )² - ( 20 )²

→ 20 a = - 400

→ a = -20 m/s²

Therefore,

Acceleration of the Bus is -20 m/s²

And, since Retardation is simply known as negative acceleration,hence

• Retardation of the Bus is 20 m/s².