IIT JEE , AIEEE Forum - Physics , Mechanics - Q.NO. - 14. FRICTION. H.C. VERMA . Plzzzzzzzz give detailed soln.

aveeral_starVirgo

The friction coefficient between a road and the tyre of a vehicle is 4/3. Find the max. incline the road may have so that once hard brakes are applied and the wheel starts skidding , the vehicle going down at a speed of 36 Km/hr is stopped within 5 m.

aditya_arora04

is the answer abt 89 degrees ????

Its a bit absurd but is it ????

aditya_arora04

Sorry, a very big blunder i made in the calclulation !!!!!!!!!!!!

The answer is 16 degrees and not 89 degrees

I heartily apologize for the confusion that i must have created. srry !!!!!!!!!

The solution is as follows :

When you make the free body diagram, you will see :

KN - mgsint = ma [ a is deceleration, t is incline, K is coeff. of friction ]

Now,

N = mgcost [ N is normal reaction ]

So,

Kmgcost - mgsint = ma

Kgcost - gsint = a

Now, usiing thrid eq. of motion,

v² - u² = -2as

100 = 2as

a = 50/s

as, s <=5

a >= 10

- gsint + Kgcost >= 10

Kcost - sint >= 1

(4/3)cost - sint > = 1

4cost - 3sint >= 3

(4/5)cost - (3/5)sint >= 3/5

sin53*cost - cos53*sint >= 3/5

sin(53-t) >= sin37

53 - t >= 37

t <= 16

Max incline 16 degrees

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