1Hmm....wel, the tension on the string 10cm abuv d block brings us 2 d ceiling only, rite?
d in dat case, i'm considerin d wt. of the string also.
so
(5+1) x 12 = 72N + 12N (coz given) = 84N.
wer m i rong?
Paragraph for Questions numbers 14 to 16 :
Mass of a string varies with its length as m = 0.1L where m is in kg and L is in cm. A block of mass 5kg is hanging to its lower end. A force F = 12 N acts on the block in vertically downward direction as shown in the figure. The entire system is kept in an elevator which moves up with an acceleration of 2 m/s^2. Length of the string is 10 cm. Height of the elevator is 4m. Assume mass of (string + mass) system to be particle like at the point of interest. Take g = 10 m/s^2.
14. Tension at a distance 10 cm above the block is
(a) 60 N (b) 70 N (c) 72 N (d) 84 N
15. Force on the string from the ceiling of the elevator is
(a) 60 N (b) 70 N (c) 72 N (d) 84 N
16. Suppose the string connecting mass to ceiling of the elevator breaks at the point P (at ceiling; see figure) after some time but the force F continues to act. The acceleration of the (string + block) system just after the string breaks assuming (string + block) system to be particle is
(a) 2 m/s2 upward
(b) zero
(c) 10 m/s2 downward
(d) 12 m/s2 downward
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UP 0 DOWN 0 0 27
27 Answers
1
1okie [3] waise sahi ho tum... question me mention karna tha... par woh meri galti nahi hai [3]
1we generally calculate wrt to ground.. if not mentioned otherwise... isnt it ?
3UR ACCN IS WRT LIFT OR WRT OUTSIDE???????????????
IF WRT LIFT ..... ITZ JUST LIKE THE BALL IS IN A PLACE HAVIN g = 12........
IF wrt ground ... then ur ans. is rite.......
1well... force 12N continues to act...
but then total force on the system = 6X10 +12 =72
so acc= 72/6 ..
why 84 ??
the upward movement of lift wont affect it .... [12]
3UR ALREADY ZOOMING INTO THE SYSTEM ..............
U CAN TAKE IT AS A SEPERATE PLACE WHICH HAS AN ACCN DUE TO GRAVITY 12 m/s2
now here when in lift we see that the point of contact is stationary wrt us .......
thus ..........T -R =0 .... R = T .......................IS ANOTHER WAY OF LUKIN AT IT ..[1]...
315 U WUDA DONE .......
84 - R = 6*2 ... RITE ............
UR ACCOUNTING FOR THE ACCN OF THE SYSTEM TWICE ..........
1I don't think. That's the prob. But sumthin 2 do wit energy conservation mayb? By a loooooooooooooooooooooooooooooooooong shot. No, i tried solvin it without d ht.
1well my ans are: 14d ,15c, 16d...
obviously not tukka... i do have reasons... but i wanna match it...
11Sorry
14
d)
T-Mg-m*lg-F=(M+m)a
T-50-10-12=6*2
T = 12+12+50+10
T = 84 N
3ARRE SAME QUESTION 2 TIMES ????? YEH KYA HUA .....KYSE HUA ... KAB HUA ... KYUN HUA ..... JAB HUA ...... OOH CHOODOO .. YEH NA SOOCHOOOO ...... [3]
1Nd, force from the ceiling means from d lift? Or is it referrin to d pt. of suspension?