6i think u shud try it urself.............
just balance fricn by centrifugal force
and N is the only unbalanced force.......
then solve...
1.a long horizontal rod has a bead which can slide along its length, the bead is initially placed at a distance L from one end A of the rod . the rod is set in angular motion in the horizontal plane about the end A with constant angular acceleration alfa . if the coefficient of friction b/w the rod and the bead is miu , and gravity is neglacted , then the time after which the bead starts slipping on the rod is
2. assertion -reasoning
st- centripetal and centrifugal forces always cancel each oher.
reason- this is because the forces act on the same body.
give explanation also
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15 Answers
61. the ans is (mu / alpha)^1/2
simple
just try to write the eqns...
2.for 2nd i think they r correct but not the correct explanation
but not sure....
6
49for number two)
The statement is wrong!! !! !! !!
centripetal force is defined from a inertial frame of reference...
centrifugal force is the pseudo force defined in a rotating frame of reference...
centrifugal force never balances centripetal force....as they never exist together on a body!!
11@ Subhomoy Bhaiya,
I have one doubt, don't they exist together in the circular motion, when the motion is describe in the non-inertial frame of reference ?
11.. 
1.
sry , this's the bst i cud drw..
let the final angular vel. be w and initial angular vel. be w1, time=t, mass=m,r=L,
now, w1=0, w=alpha*t
t=w/alpha
limiting friction= miu*mg=mw2L
miu*mg=m*(alpha)2t2L
t=√ ((miu*g)/alpha2L))
the above free body diag is from inertial frame( obviously!!!!!!!!!!)
2. both the statement and reason are individually wrong!!
as posted by Subhomoy, centripetal force is def in inertial frame and centrifugal force is the pseudo force in non inertial frame and never exist 2gether. so dont balance each other. u can only deal with 1 frame @ 1 time!!!!
71@Khyati, We don't say or assume the concept of Centripetel Force in Non Inertial or Rotating Frame. Instead we use the concept of Centrifugal Force.. Assertion --> See Post #12 (Subho)
"u can only deal with 1 frame @ 1 time!!!! " -- scintillating
Kahi apply toh nahi kar diya na. :)
@Subho, Jaha se Kuch bhi sikhne ko mile wahi main Thanks! Kehta ho.
49no
suppose in a gravity free chamber,
u rotate a stone tied to a string...
then the tension provides the centripetal force...this will be said by the man standing on the ground but the insect sitting on the revolving stone will say the tension is balancing the centrifugal force...
did u get the difference??
71Same thing... They aren't existing in same frame!!
u can only deal with 1 frame @ 1 time!!!!??
1hey scintillating why u consider gravity. don't u see the statement, gravity is neglected here
1if there is no gravity, then may be we dont have a force of friction!!! it will start sliding instantly....