Question

The driver of a car traveling 110 km/h slams on the brakes so that the car undergoes a constant acceleration, skidding to a complete stop in 4.5 sec. What is the average acceleration of the car during braking?

Answer 1

Answer: $-6.80\ ms^{-2}$

Explanation:

We know that the formula for acceleration is given by:

$a=\dfrac{v-u}{t}$ , where v = Final velocity

u= Initial velocity

Given :  The driver of a car traveling 110 km/h slams on the brakes so that the car undergoes a constant acceleration.

i.e. u=   110 km/h $=\dfrac{110\times1000}{3600}\approx35.6\ m/s$  [∵  1 km= 100 meters and 1 hour = 3600 seconds]

v=  0  m/s ( At brake , final velocity becomes 0)

t=4.5 seconds  

Substitute all the values in the formula , we get

$a=\dfrac{0-30.56}{4.5}\approx-6.80\ ms^{-2}$

Hence, the average acceleration of the car during braking is $-6.80\ ms^{-2}$.