Qualification > Sciences

How to prepare for physics paper 1(cie)??????

<< < (8/10) > >>

matabd:
Uhhh  . .
Lol i dont think i would know how to explain it easier. Thats what i think :( Sorry

halosh92:

--- Quote from: Joseph_COOL on May 18, 2010, 03:37:52 pm ---anyone plz Q22 and Q26 November O9

--- End quote ---

Q22)Y.M=STRESS/STRAIN
stress=F/A
stress=F/pie (d/2)^2
stress=20/ ( pie *(([5*10^-4])/2)^2)
strain= stress/Y.M
strain = stress(the value we calculated above substitute here)/ (2*10^11)
starin= answer A
basically the question is asking for estension/original length which is nothing but strain

matabd:
Question 22:

First use the formula E=Fl/ax (E= Young Modulus, F=Tension l = original length A=Cross sectional area and x=extension)

First find A
A=Pi/4 D^2
A=Pi/4 (5x10^-4)^2
A= 1.9635x10^-7

thus if u rearrange the formula you get x/l = F/AE
Yes ? just rearrange the above formula i gave you. Then u put in the values for F, A and E
so x/l = 20/(1.9635x10^-7)(2x10^11)

thus u get the fractional change in length, to get Percentage you want to multiply the value by 100.
So u get Answer B (x/l is just the fraction how it changes, we want to find the percentage of original length)

aldehyde1612:

--- Quote from: matabd on May 18, 2010, 03:06:09 pm ---Firstly for the Pressure One:

What i think is that Since the RHS new pressure is Patm.  - pgh and the LHS pressure is Patm+pgh. Thus the Increase is equal to RHS-LHS so you get 2pgh.


--- End quote ---

im a bit late.. but i dont get that... why did u take Patm on the LHS???
i just thought since the difference in the levels of liquid in the arms is taken as 'h' in hpg... when one side goes down by h the other side increases by h... so the difference from the level on the LHS to the level on the RHS side is 2h. ???

matabd:

--- Quote from: aldehyde1612 on May 18, 2010, 04:16:53 pm ---im a bit late.. but i dont get that... why did u take Patm on the LHS???
i just thought since the difference in the levels of liquid in the arms is taken as 'h' in hpg... when one side goes down by h the other side increases by h... so the difference from the level on the LHS to the level on the RHS side is 2h. ???

--- End quote ---


Correct. Thats what many of us, thought initially. However maybe u can say that since only the LHS increases by h, the RHS should also increase by h, thus the increase in P should just be Rho-gh. But maybe the formula actually is Delta P (change in P) = rho-g-Delta h (change in h)

Navigation

[0] Message Index

[#] Next page

[*] Previous page