Question

A car travellling with speed of 60 km/h can stop within a distance of 20 m. If the car is going twice as fast , i.e., 120 km/h, the stopping distance will be:

• A. (a) 60 m
• B. (b) 40 m
• C. (c) 20 m
• D. (d) 80 m

Answer 1

The correct option is D (d) 80 m

The correct option is D.

Given,

$u_1=60km/h,s=20m=0.02km,u_2=120km/h$

So according to the kinematic equation of the motion is:

$v^2-u^2-u62=2as$ Since $v=0$

$0-{60}^2=2\times a\times 0.02$

$a=-90000m/s^2$

Now, The speed became double

So according to the kinematic equation of the motion is:

$V^2-u^2=2as$

$0-{120}^2=2\times -90000s$

$s=\frac{-1400}{180000}$

$80m$