Physics: Post your doubts here!

[farhan141]

Using the formula you proved above, you can find E, the Kinetic Energy required to statisfy their condition.
Next, using the relation E = VQ, you can find V. This is because the kinetic energy is being provided by the electric potential energy. You already know the charge and mass of an electron from the data provided at the beginning of paper.

Thanks legend

 

[sfhn_128]

The electric field strength, E, is given by this formula:

E = F/Q (where F is force, Q is charge and E is electric field strength)

We know F = ma, so E becomes:
E = ma/q ----(i)

You're given that, K.E = k. Use the equation of K.E (1/2mv^2) to find the value of m and substitute this value of 'm' into (i)
m = 2K/v^2 ---- substituting in (i)

(i) will become:
E = ( (2K/v^2) * (a) )/ q ------(ii)

Now use the equation of motion: v^2 = u^2 + 2as
The charge starts moving from rest, so initial speed (u) is zero. And it covers a distance of 'd' for reaching plate Y, so s=d. So,
v^2 = 2ad ---- put this one into (ii)

E = ( (2K/2ad) * (a) )/ q

Simplify it, you'll get :

E = K/qd

So the answer is C.

thanks alot!

 

[Bhaijan]

This question is from a mock exam and I do not know its answer. I coudn't find the paper. And answer with the explanation would be appreciated.

 

[Rizwan Javed]

This question is from a mock exam and I do not know its answer. I coudn't find the paper. And answer with the explanation would be appreciated.
View attachment 60005
View attachment 60006

I think it's C. Because in a stationary wave, the points in adjacent loops are out phase with each other. So if the displacement of a point in one loop is S then in the adjacent loop, it should be -S.

 

[Shah34]

Hello,
Guys please solve these qs
21 C
23 C
29 D
Thanks

 

[Marinaa1998]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_4.pdf

can someone please help me with 5 b?
thanks!

 

[The Sarcastic Retard]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

can someone please help me with 5 b?
thanks!

 

[Saad the Paki]

Hello,
Guys please solve these qs
21 C
23 C
29 D
Thanks

See solution 186
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-30.html?m=1

See solution 827
http://physics-ref.blogspot.com/2015/06/physics-9702-doubts-help-page-165.html?m=1

See solution 86
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-16.html?m=1

( Physicist is it OK if I link your site? if not I'll remove it )

 

[Marinaa1998]

View attachment 60017

Thanks a lot!

 

[ashcull14]

part 2 why is WD negative in it?

 

[ashcull14]

 

[Xylferion]

View attachment 60025

You're asked to find the feedback resistances.

V out / V in = Feedback resistance / Input Resistance

They said for each switch position, V out = 1.0 V, so just plug that in for each part.

For R(A),

1.0 / 100x10^-3 = Feedback resistance of A / 1000
Feedback resistance = 10,000 ohms

For R(B),

1.0 / 10x10^-3 = Feedback resistance of B / 1000
Feedback resistance = 100,000 ohms

For V in of C, work backwards,

1.0 / V in = 1000 / 1000

V in = 1.0 Volts which is the same as 1000 mV

Hope that helped!

 

[Copy Cat]

 

[ashcull14]

You're asked to find the feedback resistances.

V out / V in = Feedback resistance / Input Resistance

They said for each switch position, V out = 1.0 V, so just plug that in for each part.

For R(A),

1.0 / 100x10^-3 = Feedback resistance of A / 1000
Feedback resistance = 10,000 ohms

For R(B),

1.0 / 10x10^-3 = Feedback resistance of B / 1000
Feedback resistance = 100,000 ohms

For V in of C, work backwards,

1.0 / V in = 1000 / 1000

V in = 1.0 Volts which is the same as 1000 mV

Hope that helped!

pretty much thanks

 

[ashcull14]

View attachment 60026

 

[ashcull14]

part 2 why is WD negative in it?

PLEASE HELP

 

[qwertypoiu]

PLEASE HELP

Change in internal energy = heat energy supplied to system + work done ON the system.

When the liquid water became water vapour, the water did work on the atmosphere, so it lost internal energy. Work hadn't been done on the system; rather the system did work. It's like a gas expanding. It does work to expand and in doing so it loses internal energy.
Basically that's why it became negative.

 

[Copy Cat]

 

[Copy Cat]

View attachment 60027

Thanks.

 

[ashcull14]

Change in internal energy = heat energy supplied to system + work done ON the system.

When the liquid water became water vapour, the water did work on the atmosphere, so it lost internal energy. Work hadn't been done on the system; rather the system did work. It's like a gas expanding. It does work to expand and in doing so it loses internal energy.
Basically that's why it became negative.

got it Thank u