Physics: Post your doubts here!

[fantastic girl]

Hello ppl
Assalamu Alaikum
http://onlineexamhelp.com/wp-content/uploads/2013/11/9702_s13_qp_11.pdf

wat is this K-CAPTURE in Q38 ?
nd i dont get 39 :/
plz someone explain

 

[fantastic girl]

View attachment 54647
How to do this one??

at the highest point, the object has no vertical velocity, but has the same horizontal velocity it had at launch

the initial KE = 1/2 m v^2 (E)

the initial horizontal velocity = v cos 45

at max height, there is no vertical velocity, so the total velocity is the horizontal velocity

therefore the KE at max height is 1/2 m (v cos45)^2 = 1/2 m v^2 0.5 --- which is half the original KE

therefore, ans is A

 

[nehaoscar]

Hello ppl
Assalamu Alaikum
http://onlineexamhelp.com/wp-content/uploads/2013/11/9702_s13_qp_11.pdf

wat is this K-CAPTURE in Q38 ?
nd i dont get 39 :/
plz someone explain

38:
It's a process by which you can capture electrons (as stated by the question)
So the +ve charge of protons will decrease by 1 as it absorbs the electron = C

39:
See 724
http://physics-ref.blogspot.in/2015/05/physics-9702-doubts-help-page-146.html

 

[qwertypoiu]

Hello ppl
Assalamu Alaikum
http://onlineexamhelp.com/wp-content/uploads/2013/11/9702_s13_qp_11.pdf

wat is this K-CAPTURE in Q38 ?
nd i dont get 39 :/
plz someone explain

K-capture is the opposite of beta-emission.
Beta-emission = one neutron turns into a proton and an electron. Result = proton number increases, atomic mass remains the same.
K-capture = electron combines with a proton and forms a neutron. Result = proton number decreases, atomic mass remains the same.

 

[fantastic girl]

38:
It's a process by which you can capture electrons (as stated by the question)
So the +ve charge of protons will decrease by 1 as it absorbs the electron = C

39:
See 724
http://physics-ref.blogspot.in/2015/05/physics-9702-doubts-help-page-146.html

Thanks

but how do u know proton number decreases by 1 ? :/
idk wth is wrong wid me...i got it when i did it before but now m not

 

[fantastic girl]

K-capture is the opposite of beta-emission.
Beta-emission = one neutron turns into a proton and an electron. Result = proton number increases, atomic mass remains the same.
K-capture = electron combines with a proton and forms a neutron. Result = proton number decreases, atomic mass remains the same.

Thankyew soo much

 

[princess Anu]

Can somebody help with any of these please:
)

 

[nehaoscar]

http://maxpapers.com/wp-content/uploads/2012/11/9702_w14_qp_13.pdf
Question number 8 - why is it A??

 

[nehaoscar]

Why D?

 

[nehaoscar]

How to do this one?

 

[nehaoscar]

How??

 

[nehaoscar]

How C?

 

[nehaoscar]

Why 2x? Because d halfes, E doubles, so x also doubles>??

 

[nehaoscar]

Thanks

but how do u know proton number decreases by 1 ? :/
idk wth is wrong wid me...i got it when i did it before but now m not

Yeah it happens always during exams that your brain just stops!
So basically it absorbs an electron right.
So an electron is negatively charged.
The nucleus has 28 protons = 28+ charge
If it absorbs one -1 charge then the charge will be 28 - 1 = 27+ charge

 

[qwertypoiu]

Can somebody help with any of these please:
)View attachment 54651View attachment 54652View attachment 54653

This should help you realise it's dcos(Θ)

As for the square wave question, I'm not sure but is it D?

There are 5 antinodes given. That represents 2 wavelengths..

2*wavelength = 293 - 14 = 279mm.
wavelength = 279mm/2 = 139.5mm = 0.1395m

f = v/wavelength = 3.0x10^8m/s / 0.1395m = 2.2GHz

 

[Mathemagical]

View attachment 54655
Why D?

Gain in Potential Energy = mgh = mgs (sin α)
Work done by engine = Fs

Efficiency = mgs (sin α)/Fs = mg (sin α)/F

 

[princess Anu]

View attachment 54660

This should help you realise it's dcos(Θ)

As for the square wave question, I'm not sure but is it D?

There are 5 antinodes given. That represents 2 wavelengths..

2*wavelength = 293 - 14 = 279mm.
wavelength = 279mm/2 = 139.5mm = 0.1395m

f = v/wavelength = 3.0x10^8m/s / 0.1395m = 2.2GHz

Thanks a lot ^.^

Btw,the ans to that ques is B ( I thought D too).. I'm attaching the screenshot of Examiner report .. see if it makes sense to you if it does then explain me too

 

[nehaoscar]

How C?

 

[nehaoscar]

Why A?

 

[princess Anu]

help please