106rohit here are the equations. Take iitimcomin's FBD
(1). Fcos30° - f1 = m.2a = 2mαR.... [as a=αR, pure rolling]
(2) f1 + f2 = Ma = MαR
(3) (f1-f2)R = Iα ==>f1-f2 = Iα/R
Add all three u get
Fcos30° = 2mαR + MαR + Iα/R
So, α = Fcos30°/(2mR + MR + I/R)
regarding ur doubt abt μN.. u dont need to wry abt it... here.. just find out max. frictional force.... but after calculations if u find that f1 > μN then there cant be pure rolling... thats y u need to take that there's sufficient friction for pure rolling.... supposing in this question μ was given as 0.5.. then max. frictional force f1 wud have been 0.5mg. if after solving the value of f1 u find that it was more than 0.5mg, then there cant be pure rolling at the surface where the disc/sphere touches the rod....
3ROHIT UVE RITTEN EVERY THIN..........
THE FIFTH EQXN IS JUST
A2 = ALPHA R ....
SOLVE EVERYTHING AND GET ALPHA........
1WHT IS THE SOLUTION>>>AFTER TAKNF RICTION FORWARD>..
62see for such cases, assume that there is no friction between the ground and the ball..
let f is the frictional force due to the top block
f=ma
a= f/m
αI=f.r
I=2/5mr2
thus,
2mr2/5α = f/m
thus, rα = 5/2f/m
thus, a-rα is -ve
so friction will be in forward direction.....
1
RAY
·2009-03-02 05:18:52
wht will be the fifth equations frenz???
62
Lokesh Verma
·2009-03-02 05:13:35
you both ahve a different direction of frictionfor the lower block
How did both of you fix the directions?
There is a standard method to do that..
3
iitimcomin
·2009-03-02 05:12:49
THEN CHUMA SOLVE EQXNS...... ULL HAVE TO TELL THE TIME AFTER WHICH W IS TO BE FOUND .. WHETHER ITS STARTIN FRM REST ETC .. SIMPLE 1 IT IS I FEEL...
1or kuch toh batao mere bhai !!!!!!1
3
iitimcomin
·2009-03-02 05:10:51
OHH U ALREADY GOT FBD ... SORRY DIDNT SEE...[2][2][2]
3
iitimcomin
·2009-03-02 05:09:59
DONT GET WORRIED ABT FRCTIONAL DIRECTION BET. GROUND AND BALL..... TAKE IT AS ANYTHIN ... IF UR DIR. IS RONG ITS VAUE WILL CUM NEGATIVE.....
I THINK U CAN MAKE TOQUES EQXNS AND NO SLIP CONDITIONS.....
1
Philip Calvert
·2009-03-02 05:09:08
btw bhaiyya are u sure that is the question there will be one more thing about max or min force i think that is why F ko angle diya gaya hai
μ * N lena hoga kahin pe........
1
RAY
·2009-03-02 05:08:43
sorry made a mistake....block is m..........spehere is M
1
Philip Calvert
·2009-03-02 05:05:47
ok jokes over..........
assuming it to be same as the ones i solved................
Fcos θ lo friction ground se or upar wale se.........
now remember upar wale ka acc = 2acom bus....
ya fir truck [1]
any trick or diff from conventionality i cannot see rite now...
dazed head after spoiling english paper.[4]
haha english is not in dictionary over here
62
Lokesh Verma
·2009-03-02 05:03:40
@philip..
na there is ground below too :P
62
Lokesh Verma
·2009-03-02 05:03:13
@philip.
take m and M and R
It has enuf friction on both surfae to make pure rolling.
1
Philip Calvert
·2009-03-02 05:02:14
my answer w =0 as the ball will fall down bcoz it is floating in the air right now or agar..
bar magnet hai or ye magnetic ya metal cylinder toh sochna padega [9]
