Question

On a foggy day, the two cars are approaching each other on a straight road, with speeds `72 km h^(-10` and `54 km h^(-1)`. The drivers of the cars spot other when they were `60` meres apart. Both of them applied brakes, retarding their cars at of `6 ms^(-1)`. Predict whether they will avert collision or not.

Answer 1

For the first car, `u=72 km h^(-1) =20 ms^(-1) , v=0, a =- 6 ms^(-2) , S=s_(1)`
As, `v^(2) -u^(2) =2 aS`
:. `0^(2) -(20)^(20 =2 2 xx (-6) s_(1)`
or `s_(1) =(400)/(12) =33.33 m`
For the second car, `u=60 km h^(-1):
`=(60 xx5)/(18) =15 ms^(-1)`:
`v_(0, a=- 6 ms^(-2) , S=s^(2)`
As, `v_(2) -u^(2) =2 aS`
:. (0) ^(2) -(15)^(2) =2 (-5) s^(2)`
or `s_(2) =(225)/(12) =18 .72 m`
Total distance coverd by two cars
``=-s_(1) +s_(2) =33.33 +18.72 =52.08 m`
As this distance is less than the collision will be averted.