You are Here: Home >< Physics

# The Physics PHYA2 thread! 5th June 2013 watch

• View Poll Results: What mark do you think you got out of 70?
0-20
6
3.00%
21-40
12
6.00%
41-50
29
14.50%
51-60
79
39.50%
61-70
74
37.00%

1. (Original post by StalkeR47)
LOOL !
2. The great guy!
3. (Original post by Jimmy20002012)
Wrote literally the same thing as you

Posted from TSR Mobile
LOL!!!!
4. (Original post by NedStark)
For the count the squares under the line trick, what's the the general method of part sqaures. Do we consider them as halves or something?
5. (Original post by planck)
I've seen a past paper question somewhere about springs in parallel and springs in series.

Basically parallel spreads the extension between the two springs since the force is shared.

And for series each spring extends by what you'd expect meaning that the overall extension is double that for one spring.
Thanks!!
6. Is there a list of the formulas needed for this exam out there? Or are they all on the formula sheet?
7. (Original post by looloo4)
Is there a list of the formulas needed for this exam out there? Or are they all on the formula sheet?
Some formulas will not be in the formula sheet.
8. (Original post by StalkeR47)
Some formulas will not be in the formula sheet.
Is there a list anywhere? because there are a lot of irrelevant formulas in the text book and it would be a waste of time learning all of them?
9. (Original post by StalkeR47)
Lots of smiles to you! Since work done = force time (THE DISTANCE IN THE DIRECTION OF THE FORCE), you will have to workout the horizontal force and times it by the distance travelled which is 1x10^3m. Is that ok? And are you a Muslim? Thanks.
hmm sorry i'm not quite sure- doesnts 170000cos40 calculate the vertical force and tan would be used to calculate horizontal? confused
and not Muslim no, what made you think that? and why?!
10. Nahhh I like the trapezium rule
11. In phya2/jan12, for 1(c) they don't accept spring constant of the cable or work lost on the cable :'(
12. (Original post by taliaa)
hmm sorry i'm not quite sure- doesnts 170000cos40 calculate the vertical force and tan would be used to calculate horizontal? confused
and not Muslim no, what made you think that? and why?!
Hey calm down! I did not wanted to offence you ok? But if I did, I am really sorry! For this question, 170kcos40 gives a horizontal not vertical force. Since 1km is in the horizontal direction, you will have to find the horizontal force. Does that make sense? If not, tell me and I will draw a diagram for you. BTW you are very horrible!
13. (Original post by looloo4)
Is there a list anywhere? because there are a lot of irrelevant formulas in the text book and it would be a waste of time learning all of them?
There is no list. They actually try to show you where they got the equation from that is why it looks like as if there are lot of formulas to learn. I have learnt all of them anyway. Learn this one. Maximum number of order is given by n=d/lambda where d is the slit spacing. Sorry, this is the only one I can think of now. Will tell you more if I can remember.
14. I dont get any of this unit ... i've completed all the past papers and i'm just failing :'( :'(
15. (Original post by ammara_12)
I dont get any of this unit ... i've completed all the past papers and i'm just failing :'( :'(
What have you been getting on the past papers?
16. (Original post by StalkeR47)
What have you been getting on the past papers?
like c's :'( I don't get any of the optics stuff! and I keep using the wrong suvat equations
17. (Original post by ammara_12)
like c's :'( I don't get any of the optics stuff! and I keep using the wrong suvat equations
Do you need any help? On anything at all? I can help you now.
18. (Original post by ammara_12)
like c's :'( I don't get any of the optics stuff! and I keep using the wrong suvat equations
not sure if this will help, but i posted it earlier:

Here are some key points i made for all of you for PHYA2 to bare in mind:

• Forces acting on an object in equilibrium form a closed loop (Vector triangle)
• Define moment: force x perpendicular distance, and is the turning effect of a force around a turning point.
• Principle of moment: For a body to be in equilibrium, the sum of the clockwise moments about any point equals the sum of the anticlockwise moments about the same point.
• Torque = Force (Turning force) x perpendicular distance between them.
• gives the gradient on a curve to be velocity. and since is acceleration, therefore the stepper the curve the greater the acceleration.
• Newton's First Law: An object will stay at rest or in uniform velocity, unless a resultant foce acts on it.
• Newton's Second Law: Acceleration is proportional to the resultant foce acting on it at a certain mass. F=ma
• Newton's Third Law: When 2 objects interact, they exert an equal and opposite force on eachother.
• Free fall is when the only force acting on an object is gravity.
• For projectile motion: VERTICAL you use SUVAT, for HORIZONTAL you use and in both cases 't' is the same.
• When Friction force = Driving Force object stops accelerating and reaches its terminal velocity.
• Types of friction: Contact (Friction), Fluid (Drag, Air resistance, Fluid Resistance)
• Principle of conservation of energy: Energy cannot be created or destroyed, but can be transferred from one form to another.

• Hooke's Law: Extension is proportional to force given it is within the limit of proportionality.
• Experiment to investigate extension:

1) Object should be supported using a G-clamp
​2) Measure original length using a ruler
3) Masses should then be added in 100g intervals up to atleast
600g.
4) For each mass added, calculate new extension using (new
length - original length).
6) Repeat experiment 3 times taking an average result.
7) Plot a graph of force against extension to show results.

• Young Modulus:
• Young's Experiment:

1) Set up experiment.
2) Add enough mass to straighten wire but not extend it.
3) measure original length using a ruler
4) Add in intervals of 100g of mass up to what it could withstand, and for each mass added read off the new length by using a travelling microscope or vernier calliper.
5)calculate extensions by using (new length - original length)
6) Measure cross sectional area using , to obtain D, you would used a micrometer and measure at different positions on the wire and take an average reading.
7) Repeat experiment 3 times
8) plot a graph of stress against strain and gradient will give young modulus or Young Modulus = .

• Waves are vibrations, they only carry and transfer energy.
• 4 things a wave can do:

1) Reflect - Wave bounces back when hitting a boundary.
2) Refract - wave direction changes as it enters a medium
3) Diffract - wave spread out
4) Interfere - 2 waves co-join

• Phase difference: Amount by which one wave lags behind another wave.
• Transverse waves: Vibrations oscillating at right angles to the direction of travel (Electromagnetic waves, waves on rope, ripple of water ...etc)
• Longitudinal waves: Vibrations oscillating along direction of travel (sound)
• Application of polarisation: Glare reduction (polaroid sunglasses). Improving TV and radio signals by lining up the rods of the receiving aerial to the transmitting aerial.
• Optical fibres: light in optical fibres is used to transmit phone and cable TV signals. Light doesn't heat up fibre therefore little energy loss. No electrical interference. and it is a cheaper alternative.
• Signal loss (reduction in amplitude) in optical fibres are caused by energy lost through absorption and scattering.
• Signal broadening is caused by multi-path dispersion which is when the signal travels straight down the middle and arrives earlier than those undergoing T.I.R.
• Principle of Superposition: When 2 or more waves cross, the resultant displacement equals the vector sum of the individual displacement.
• Constructive interference: when displacement combine to make an even bigger one (e.g. crest plus crest)
• Destructive interference: when negative and positive displacement combine to cancel out (e.g. crest plus trough)
• Stationary or standing wave: is the superposition of two progressive waves with the same frequency and amplitude travelling in opposite directions towards each other. this is when you get fundamental frequency which is . if you double the fundamental frequency you get the second harmonic (first overtone). Triple the fundamental you get third harmonic (second overtone) and so on ...
• Fundamental frequency depends on the length, mass and tension of a spring.

1) if length increases, frequency decreases
2) if mass increases, frequency decreases
3) if tension increases, frequency increases

• Application of stationary waves: Microwaves, sound waves.
• you get greatest diffraction if the slit size is equal to
• Laser is monochromatic (has a single wavelength) and coherent (same frequency and constant phase difference).
• laser beams are powerful and can cause damage to eyesight, this can be prevented by wearing safety laser goggles or removing any reflective surfaces.
• Path Difference: how much further a wave has travelled than the other wave.
• When you get constructive interference, at your first order(s) [bright fringes] your path difference is where is an integer this also means that the phase difference is a multiple of .

• where you get [dark fringes] between say zero and the first order or first and second order, the path difference is where the phase difference is a multiple of (for it to be perfectly out of phase).
• non - coherent light such as white light will have wider maxima containing different colours with central white fringe. light is continuous range of frequencies
• Young's double slit experiment: . w is fringe spacing. is wavelength, s is spacing between slits, and D is distance from slits to screen.
• Diffraction grating: They have more slits causing bright bands to be brighter and narrower and dark fringes to be even darker. monochromatic light is used causing interference patterns to be sharper and more accurate of a measurement.

Hope it helps !!!!!
19. (Original post by StalkeR47)
Do you need any help? On anything at all? I can help you now.
could you explain the youngs modulus experiment to me please

actually its ok someone posted notes on it

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: September 15, 2013
Today on TSR

### The most controversial member on TSR?

Who do you think it is...

### Is confrontation required?

Discussions on TSR

• Latest
Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE