Answer:
(c) is the correct option.
Explanation:
Given that,
Initial velocity, u = 56 mi/h and 28 mi/h
Final velocity, v = 0
It is coming to rest it means it is under deceleration. So, it will be (-a). Using the third equation of motion as folows :
[tex]v^2-u^2=2as[/tex]
So,
[tex]0-(56)^2=2(-a)\times s\\\\s=\dfrac{3136}{2a}\\\\s=\dfrac{1568}{a}\ ....(1)[/tex]
Also,
[tex]0-(28)^2=2(-a)\times s'\\\\s'=\dfrac{784}{2a}\\\\s'=\dfrac{392}{a}\ ....(2)[/tex]
Dividing equation (1) by (2)
So,
[tex]\dfrac{s}{s'}=\dfrac{\dfrac{1568}{a}}{\dfrac{392}{a}}\\\\\text{s is same for both cases}\\\\\dfrac{s}{s'}=4\\\\s=4\times s'[/tex]
So, we will travel 4 times farther if braking from 56 mi/h to rest than from 28 mi/h.
