Physics: Post your doubts here!

[farhan141]

Hello , may anyone please give a website i can revise the chps from and advise me with some past papers i should do !

ThQ in advance .

www.studyguide.pk

 

[princess Anu]

can somebody explain how is the answer for C : 7.4?​

 

[princess Anu]

the ques is is given in pink ( just beside the highlighted ans)
my question is can we give a similar answer interms of potential differen rather than currect? about how pd across external circuit wud decrease bcz of less effective resis now therefore more power will be dissipated in the internal resist of the battery? or will that be not credited?

 

[Boss201]

Explain, in terms of the air molecules, why the pressure at the top of a mountain is less
than at sea level ?

 

[Abeha Malik]

can anyone plz provide me with some good physics revision notes ????

 

[amal sharkawi]

Can anyone answer this question plz ??

 

[forest822]

Can anyone explain why it is not appropriate to use the Young Modulus to determine the extension when the braking force is applied? Thank You.

 

[eliyeap]

Explain, in terms of the air molecules, why the pressure at the top of a mountain is less
than at sea level ?

Because the density of the air varies. As you go up the mountain, the air gets thinner meaning the no. of air molecules decreases. For pressure, the air molecules collide with one another as well as with the wall of the container. When they collide they experience a change in momentum which in turns produces a force. Pressure is given by the average of this combine collective forces. Hence, the lower the no. of molecules the lower the pressure.

 

[eliyeap]

View attachment 53300 can somebody explain how is the answer for C : 7.4?​

Weight - F=ma
(2.3*9.81) - (0.042* 12^2)= 2.3(a)
23-6.048=2.3(a)
a=7.4 ms^-2

Basically the weight of the object is pulling it downwards while the friction is acting upwards. If the weight is more than the friction then you get an acceleration. Hope you get it!

 

[eliyeap]

Can anyone explain why it is not appropriate to use the Young Modulus to determine the extension when the braking force is applied? Thank You.

Because at the breaking force, the extension is no longer proportional to the force applied, that is hooke's law is no longer obeyed.

 

[princess Anu]

J 2012/22 Q6b
The Examiner report says,' many omitted the adjustments to obtain resonance' :/ I don't get it what is resonance & how do we obtain a reading for it??
Please HELP

 

[The Chill Master]

M/J/2002/P4
Q4 (b) and (c) part can anyone explain?

 

[DESTROYER1198]

does anyone know any good physics revision notes

 

[amal sharkawi]

Can anyone answer this plz??

 

[forest822]

Because at the breaking force, the extension is no longer proportional to the force applied, that is hooke's law is no longer obeyed.

Thank your for the solution. How's Hooke law is related to Young Modulus? Thank You.

 

[Furqan Azam]

Whenever I do a vector question, I stuck on it. Latest one is from Nov 2014. It will be nice if someone can draw the diagrams of Q`1 c i, ii. Thanks.

 

[Xylferion]

Whenever I do a vector question, I stuck on it. Latest one is from Nov 2014. It will be nice if someone can draw the diagrams of Q`1 c i, ii. Thanks.

Look for my post here: https://www.xtremepapers.com/commun...st-your-doubts-here.9860/page-658#post-899092

 

[princess Anu]

is this correct?!

 

[Sarosh Jameel]

Can someone plz help me to derive pressure=density*gravity*height !!!

 

[eliyeap]

Thank your for the solution. How's Hooke law is related to Young Modulus? Thank You.

Young modulus is the gradient for the graph of stress against strain. Normally, when we measure the Young Modulus we take it from the proportional limit, that is the straight line part of the graph. This straight line part denotes the max load for which hooke's law is obeyed and is also the place where elastic deformation occurs. I hope that answers your question! Maybe you should look at the graph for ductile materials for a better understanding.