IIT JEE , AIEEE Forum - Physics , Mechanics - QUESTION IN MECHANICS....RATES ASSURED......

zamuka

a uniform sphere of mass m & radius r rolls without slipping down an inclined plane set at an angle $\alpha$ to the horizontal. find

a) magnitude of friction coeff at which slipping is absent.

b) the kinetic energy of the sphere t seconds after the beginnning of motion.

ANS: a) $\mu$ $\ge$ 2/7* tan $\alpha$

b) 5/14* mg²t² sin² $\alpha$

got the a) part....... plz explain the other part...

RATES ASSURED

varun.tinkle

I AM NOT SURE WETHER ITS RIGHT OR WRONG
SINCE THERE IS NO SLIPPING
F*R=IA
FROM THERE U CAN FIND OUT A A
AND KINETIC ENERGY=1/2MV^2+1/2IW^2
THE ONLY DOUBT IN MY MIND IS THAT
WHAT WILL BE THE VALUE OF U

ashish_banga

the value of mu when no friction is acting is given by =

$\mu \le \frac{tan\theta}{1 +\frac{m{r}^{2}}{I}}$

varun.tinkle

HOW DO U KNOW THAT

shreyasnivas

I can explain, but u do the question and see.

if there is rolling without slipping, then there will be no energy loss becos even though friction IS actiong, it is not eating up any energy.

the rest is easy.. write force and torque eqns and find the angular or linear acceleration.

a = r $\alpha$ since no slipping. then say that a = dv/dt , and integrate to find velocity as a function of time.. the kinetic enery is = the sum of translational and rotational KE. that is 1/2 mv² + 1/2 I w²

wr = v (no slipping) and you know v.

so thats it..

Ask & Discuss Questions with Community & Experts