Physics: Post your doubts here!

[hassam]

Re: Physics Help here! Stuck somewhere?? Ask here!

well....i read this strange line in physix course book....that when u compress a gas it becomes hot....in other words its internal energy increase.....bt if work is in done on the gas as in this case....shud not the internal energy decrease cos molecule gets closer so potential energy becomes more -ve

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

Help J04/P1/Q.9,Q.17,Q.18,Q.31

Q9) speed at take off only consists of horizontal component as vertical component is zero,
so u= s/t = 10/t horizontal component remain constant throughout

now find the time taken to land, considering the vertical motion
s=ut+1/2gt^2
1.25=0(t)+1/2(-9.81)t^2
t=0.5 s

u=10/t = 10/0.5 = 20 ms^-1

Q17)
let the speed and mass of car Y be v and m respectively
KE1=1/2mv^2

Car X has v/2 speed amd 2m mass
KE= 1/2(2m)(v/2)^2
KE=m(v^2/4)
KE2=1/4mv^2

so KE2=1/2 KE1

Q18)
WD= gain in PE
WD= mgh= 50(9.81)(1.6)= 784.8= 780 J

Q31)
I is proportional to 1/R
and R is proportional to pl/A
so I is also proportional to 1/(pl/A)= A/pl where resistivity and length is constant
so I is proportional to A

I in Q/ I in p= {pi(2/2)^2}/{pi(1/2)^2} pi cancels
= 1/(1/4)
= 4

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

N04/P1/Q5,16,20

Q5)
T (time period)=1/f
T=1/50 = 0.02 = 20 ms

because one time period (1 complete wave) covers 8 boxes (8 cm) on x axis,
so for 1 box= 20/8 = 2.5 mscm^-1

Q16)
gain in KE= WD on the box - WD by the friction
=90(6) - 50(6) = 240 J

Q20)
pressure at x distance above the bottom is same for both P and Q

pressure of P= Po + Ppg(2x) where Po is atmosphereric pressure

pressure at Q= Po + Pqgx

Po + Ppg(2x) = Po + Pqgx Po and g cancel
Pp/Pq=x/2x= 1/2

 

[destined007]

Re: Physics questions? please?

Question 10 Please.

Thanks!

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

well....i read this strange line in physix course book....that when u compress a gas it becomes hot....in other words its internal energy increase.....bt if work is in done on the gas as in this case....shud not the internal energy decrease cos molecule gets closer so potential energy becomes more -ve

When a gas is compressed, work is done on the gas molecules. This means that additional energy is transferred to the gas molecules from whatever is doing the compressing. It is the additional energy that increases the kinetic energy of the molecules. Now because KE increases internal energy also increases. Decrease in PE is insignificant.

 

[darkpichu]

Re: Physics questions? please?

Question 10 Please.

Thanks!

hello i don't understand why you used 2x instead of x in I^0=I exp^(-ux)

Please clarify.

 

[destined007]

Re: Physics questions? please?

Question 10 Please.

Thanks!

hello i don't understand why you used 2x instead of x in I^0=I exp^(-ux)

Please clarify.

because wave traveled from surface to the fat-muscle boundary and from fat-muscle boundary back to surface. That makes x + x= 2x.

 

[mufc102]

Re: Physics Help here! Stuck somewhere?? Ask here!

J04/P2/Q.1 (B), Q.2 (B)
J05/p1/Q.3,4,11,20,22,24,32,33,36
and thanks for the previous solutions

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

can someone kindly post the notes on momentum by naushad or any other good teacher ??

why don't you take tuition from him?

 

[Abdulrab]

Re: Physics Help here! Stuck somewhere?? Ask here!

if u have notes then just post them !!! you dont hav the right to tell me to take tutions or not !!! :O

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

I do have freedom of speech, so the right to speak.
Anyway, I wasnt ordering you rather advising. Its better you go to naushad because it's teachers on the spot explanation that matters.

 

[hassam]

Re: Physics Help here! Stuck somewhere?? Ask here!

1.explain in terms of kinetic energy,why temperature of a stone increases when it falls from a cliff and lands on the beach below?
2.Explain why the barrel of bicycle pump gets very hot as the pump is used to pump a bicycle tyre

 

[kandelbiz]

Re: Physics Help here! Stuck somewhere?? Ask here!

in a time period of 8 minutes 3.6*10^16 chloride(Cl-)ions are neutralised and liberated at the anode and 1.8*10^16 copper(Cu2+) ions are neutralised and deposited on the cathode.
1. Calculate the total charge passing through the electrolyte in this time

 

[rz123]

Re: Physics Help here! Stuck somewhere?? Ask here!

if u have notes then just post them !!! you dont hav the right to tell me to take tutions or not !!! :O

that's very rude of you, he is helping you and in return you are replying in a bad manner. you could have disagreed in a better way. :fool:

 

[princesszahra]

Re: Physics Help here! Stuck somewhere?? Ask here!

back to the topic everyone!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
i don't have any doubts in physics!

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

1.explain in terms of kinetic energy,why temperature of a stone increases when it falls from a cliff and lands on the beach below?
2.Explain why the barrel of bicycle pump gets very hot as the pump is used to pump a bicycle tyre

while falling speed increases, air resistance increase, temp increase. When its hits the ground, there is a sudden increase in the motion of the stone particles with raises the internal KE, increasing its temp.

pressure builds up. Higher collisions. increased speed. increased KE. increased temp.

 

[destined007]

Re: Physics Help here! Stuck somewhere?? Ask here!

in a time period of 8 minutes 3.6*10^16 chloride(Cl-)ions are neutralised and liberated at the anode and 1.8*10^16 copper(Cu2+) ions are neutralised and deposited on the cathode.
1. Calculate the total charge passing through the electrolyte in this time

2Cl-1 -------> Cl2 + 2e-

moles of Cl-= (3.6x10^16)/(6.02x10^23)= 6x10^-8 mol

charge= 6x10^-8 x 96500=5.79 x 10^-3 C

 

[rz123]

Re: Physics Help here! Stuck somewhere?? Ask here!

http://www.xtremepapers.com/CIE/Interna ... _qp_11.pdf

Q.9 , 13, 22, 34 kindly help!

 

[abcde]

Re: Physics Help here! Stuck somewhere?? Ask here!

I'm having a little doubt in vector components. Consider this: A trolley of weight, W, 600 N is going down a slope, which is at an angle of 30* to the horizontal. They say that the component of W down the slope is = W sin 30*. How is that? The way I'm thinking it should be W/sin 30*. I'm obviously wrong. Can anyone explain why?
Thank you.

 

[abcde]

Re: Physics Help here! Stuck somewhere?? Ask here!

I'm having a little doubt in vector components. Consider this: A trolley of weight, W, 600 N is going down a slope, which is at an angle of 30* to the horizontal. They say that the component of W down the slope is = W sin 30*. How is that? The way I'm thinking it should be W/sin 30*. I'm obviously wrong. Can anyone explain why?
Thank you.

It's partially urgent!