An automobile approaches a barrier at a speed of 20 m/s along a level road. the driver locks the brakes at a distance of 50 m from the barrier. what minimum coefficient of kinetic friction is required to stop the automobile before it hits the barrier?

μ = 0.408

Explanation:

given,

speed of the automobile (u)= 20 m/s

distance = 50 m

final velocity  (v) = 0 m/s

kinetic friction = ?

we know that,

v² = u² + 2 a s

0 = 20² + 2 × a × 50

a = 4 m/s²

We know

F = ma = μN

ma = μ mg

a = μ g

μ = 0.408

hence, Kinetic friction require to stop the automobile before it hit barrier is 0.408

do you have a formula possibly

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min