Physics: Post your doubts here!

[Darth Vader]

Thnx BATA

 

[Konstantino Nikolas]

View attachment 59592 View attachment 59592
The examiner report says that the gradient is NOT the reciprocal of resistance. The ans is A. Can someone explain the reasoning behind this? And if the gradient is not the reciprocal of resistance then what does it represent?

Resistance is the inverse of the gradient ONLY if the graph is a straight line through the origin, i.e, when the resistance is constant. Ohmic conductors (ex: metal wires) show this relationship.

 

[leenz98]

??

For your first question A will be on the upper side of the region of field where the 1cm thing is written and B will be on the he lower line of the box next to the region of field and both come from Flemings left hand rule.

 

[leenz98]

??

for s05 6b, it follows from the current graph that as current varies in magnitude and direction the magnetic flux changes so the shape of the graph will be the same as that of the current and since induced emf is directly proportional to rate of of change of magnetic flux completing as many cycles as current in the first and shape is also same.

 

[leenz98]

??

for s05 6b, it follows from the current graph that as current varies in magnitude and direction the magnetic flux changes so the shape of the graph will be the same as that of the current and since induced emf is directly proportional to rate of of change of magnetic flux completing as many cycles as current in the first and shape is also same.
For s07 3b, I dont think there is any other way to do it. In fact divide the area under the graph into a geometrical shape and find the value for it and then for the curved part find the value of 1 box and count the boxes as accurately as you can.
For question 6a I think, you just need to know the general things about simple harmonic and then mould your answer according to the questions. Say the the motion is vibratory or to or fro and the magnet accelerates towards the mean position and since the magnet comes to rest after a few oscillations you can say that damping occurs. For the second part of the same question, I think that as resistance increases the current flowing in coil decreases and magnetic field around wire weakens and hence interacts lesser with the magnet's field so damping occurs slowly. ( not sure about this tho)

 

[The Sarcastic Retard]

For your first question A will be on the upper side of the region of field where the 1cm thing is written and B will be on the he lower line of the box next to the region of field and both come from Flemings left hand rule.

I got that. I was asking which will deflect more.

 

[The Sarcastic Retard]

for s05 6b, it follows from the current graph that as current varies in magnitude and direction the magnetic flux changes so the shape of the graph will be the same as that of the current and since induced emf is directly proportional to rate of of change of magnetic flux completing as many cycles as current in the first and shape is also same.
For s07 3b, I dont think there is any other way to do it. In fact divide the area under the graph into a geometrical shape and find the value for it and then for the curved part find the value of 1 box and count the boxes as accurately as you can.
For question 6a I think, you just need to know the general things about simple harmonic and then mould your answer according to the questions. Say the the motion is vibratory or to or fro and the magnet accelerates towards the mean position and since the magnet comes to rest after a few oscillations you can say that damping occurs. For the second part of the same question, I think that as resistance increases the current flowing in coil decreases and magnetic field around wire weakens and hence interacts lesser with the magnet's field so damping occurs slowly. ( not sure about this tho)

Thanks.

 

[The Sarcastic Retard]

c(ii) and d.
anyone?

 

[Darth Vader]

I want the solution for this
The answer is D

 

[Rizwan Javed]

View attachment 59607
I want the solution for this
The answer is D

First find the time taken for the stone to reach the water surface. This can be found by using the equation of motion: s = ut + 0.5at^2
s is 78 m, u is zero since it is dropped from rest and a is 9.81 m/s^2

Substitute these values into the equation and solve for 't'. You'll get t = 3.99s.

Then find the time taken for the sound waves to reach the person. This can be found by : t = s/v
t = 78/330 = 0.236s

Add these two times calculated: 0.236 + 3.99 = 4.226 ~ 4.22s

So the answer is D.

 

[Darth Vader]

First find the time taken for the stone to reach the water surface. This can be found by using the equation of motion: s = ut + 0.5at^2
s is 78 m, u is zero since it is dropped from rest and a is 9.81 m/s^2

Substitute these values into the equation and solve for 't'. You'll get t = 3.99s.

Then find the time taken for the sound waves to reach the person. This can be found by : t = s/v
t = 78/330 = 0.236s

Add these two times calculated: 0.236 + 3.99 = 4.226 ~ 4.22s

So the answer is D.

Thnx mate

 

[sj0007]

Can anyone explain this? The answer is D

 

[Darth Vader]

Can anyone explain this? The answer is D
View attachment 59608

A standing wave is produced when two waves are moving in opposite direction to each other which have the same frequency, wavelength and speed. So when the two loudspeaker are positioned in opposite direction a standing wave is produced

 

[The Sarcastic Retard]

View attachment 59605
View attachment 59606
c(ii) and d.
anyone?

?

 

[Saad the Paki]

Please someone explain this I have no idea how to do this.

 

[sj0007]

A standing wave is produced when two waves are moving in opposite direction to each other which have the same frequency, wavelength and speed. So when the two loudspeaker are positioned in opposite direction a standing wave is produced

Ummm okay........ But what I don't get is why isn't it B or C then?
Since B has two speakers in the opposite directions and C has a reflection (which in the question is set up).........

 

[sj0007]

View attachment 59612
Please someone explain this I have no idea how to do this.

I don't think I have the proper explanation behind it but how I did it was that x+y has to be 50 and x has to be the smaller one......... This leaves us with only option B.......... And I think the answer is B ?

 

[Saad the Paki]

I don't think I have the proper explanation behind it but how I did it was that x+y has to be 50 and x has to be the smaller one......... This leaves us with only option B.......... And I think the answer is B ?

So is C. X+Y is 50. And don't say that X is smaller in the diagram cuz it's not to scale and yes the ans is B

 

[sj0007]

So is C. X+Y is 50. And don't say that X is smaller in the diagram cuz it's not to scale and yes the ans is B

Oh I never noticed the Not to scale thing..........
Like I said, I don't think I have a proper explanation but I guess it has something to do with the excess pressure and stuff

 

[Maayee]

can someone pls help me with this..
http://papers.gceguide.com/A Levels/Physics (9702)/9702_w15_qp_43.pdf
Q10 a an b and also 12 c