The Physics PHYA2 thread! 5th June 2013

Could anyone explain to me the procedure to find the wavelength of the laser light?

what is the definition for Ultimate tensile stress?

I heard its the stress needed to break a material, but when I look on some graphs, it shows the material extending after the ultimate tensile stress point is reached, how can it extend if its already broken?

Ultimate tensile stress is indeed, what you have defined. It is the tensile stress needed to break a solid material. But when it says 'stress needed to break a solid material', it means, the stress needed to start breaking a solid material.

So, for example, with a wire, the ultimate tensile stress is the point at which the wire is being extended at its WEAKEST point, thus, any further extension will cause it to BREAK. So, think of it as the point beyond which if a solid is subject to any more stress, it will break.

Reply 922

x-Sophie-x

13

Original post by StalkeR47

HAHA! There was yes! It took me dam 10 mins to find to find that question just now. :smile:

It was on jan 11 Q 1bi. :smile:

Why thank you! :h:

How kind

I'd rep, but it won't let me :/

Reply 923

posthumus

20

Original post by RU486

How would I do 6bii on June 12?

Time period is time taken for 1 oscillation... you want it for quarter of an oscillation.

T= 1/frequency

then divide T by 4

Reply 924

StalkeR47

5

Original post by x-Sophie-x

Why thank you! :h:

How kind

I'd rep, but it won't let me :/

Oh it is alright! :smile:

Thank you! :smile:

Reply 925

username1201943

19

I'd rather not do the exam tomorrow.........................

Reply 926

Raimonduo

Original post by Pirateprincess

I agree that one of the wave ones seems like the most likely option. However, it seems that this year the examiners are trying to be creative across all the boards, so thus far I have found that "expect the unexpected" is a phrase to live by (I mean, look at the six-marker for unit 1). SO... the real question is what would you least expect?

If that's the case. I'm gonna say one thing, the 6-marker will probably be on the derivations we need to know. I suggest everyone brush up on them, specifically the energy stored in a spring, as spring stuff really hasn't been in a lot of 6-markers yet. My guess is it will be something to with how you would calculate the energy stored in a spring and the work done by it.

Reply 927

mikey2912

Original post by StalkeR47

if you do not like physics, why did you pick physics then?

i picked the four subjects i got a* in, and i think physics is a good a level to have

Reply 928

Pirateprincess

2

Original post by Edorrans

Could anyone explain to me the procedure to find the wavelength of the laser light?

That depends on what the question is exactly. IF they tell you the frequency then rearrange v=fλ to get λ= v/f, where v is the speed of light (3.00x 10^8 ms^-1)
If you're using the laser for a double slit experiment then rearrange spacing of maxima= wavelength x distance from slits to screen slit spacing

You could use a number of other methods but it depends on what info they give you. Did you have a specific question in mind?

Reply 929

StalkeR47

5

Original post by mikey2912

i picked the four subjects i got a* in, and i think physics is a good a level to have

Congratulations Then. :smile:

Reply 930

FLLF

Original post by Jack93o

what is the definition for Ultimate tensile stress?

I heard its the stress needed to break a material, but when I look on some graphs, it shows the material extending after the ultimate tensile stress point is reached, how can it extend if its already broken?

Its the point on the stress strain curve with the highest stress

Reply 931

masryboy94

8

Original post by SortYourLife

PAST PAPER MARKS:

Jan 10: 58 - 116 UMS
June 10: 60 - 120 UMS
Jan 11: 59 - 114 UMS
June 12: 62 - 120 UMS
Jan 13: 54 - 105 UMS

Hoping papers nicer than the Jan 13 one. Last question wasn't nice

Posted from TSR Mobile

well done ! ... yeh i am hoping so too :redface:

Reply 932

Lester95

Original post by Raimonduo

If that's the case. I'm gonna say one thing, the 6-marker will probably be on the derivations we need to know. I suggest everyone brush up on them, specifically the energy stored in a spring, as spring stuff really hasn't been in a lot of 6-markers yet. My guess is it will be something to with how you would calculate the energy stored in a spring and the work done by it.

Good idea! I assume you'd derive the equation from Work = Force x Displacement and just go from there? I lose so many simple marks I need to do well on the 6 marker :s-smilie:

Reply 933

masryboy94

8

Original post by StalkeR47

like this! The bottom spectrum. :smile:

so for the white light being diffracted, you don't get no dark fringes? just a continuous spectrum, right?

Reply 934

Jack93o

15

Original post by Raimonduo

Ultimate tensile stress is indeed, what you have defined. It is the tensile stress needed to break a solid material. But when it says 'stress needed to break a solid material', it means, the stress needed to start breaking a solid material.

So, for example, with a wire, the ultimate tensile stress is the point at which the wire is being extended at its WEAKEST point, thus, any further extension will cause it to BREAK. So, think of it as the point beyond which if a solid is subject to any more stress, it will break.

but it doesn't get subjected to any more stress after the UTS (ultimate breaking stress) point, the line on the stress-strain graph actually slopes downwards, showing an increase in extension for a decrease in stress

Reply 935

Solivagant

18

Original post by UnknownRoyalist

I'd rather not do the exam tomorrow.........................

I'm with you on that. It's going to be awful.

Reply 936

masryboy94

8

Original post by wallaby

So I draw it basically as a straight line along the curved path of the ball, in the direction of the resultant velocity? :smile:

yeppp

Reply 937

SAS18

10

so how do you know how many sig figs answer you should give? cos it keeps changing in the markscheme

Reply 938

mikey2912

Original post by StalkeR47

Congratulations Then. :smile:

thankyou

hahaha

Reply 939

x-Sophie-x

13

For the optics topic, in the core of an optical fibre, if total internal reflection/refraction doesn't happen, then does the reflected ray always reflect at the same angle as the angle of incidence?

For example, question 4, June 2012.

Angle of incidence=Angle of refraction=85 degrees. Is this always the case?

The Physics PHYA2 thread! 5th June 2013

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