Final Physics(h) Preperation

stevoxbx

Try use this thread just to keep all the physics questions-predictions and all the rest together.

Im trying to do an awful lot of the course over the next 2days. Topics im gona know inside out hopefully are:

Particle Physics (Has to come up. 15%)
All of electricity (2 questions come up a year, thats roughly 30% and its only a few chapters, mostly understanding)
Experiments (Lets face it there not that hard, only 20 or so of em. Know the formulas, the graphs + precautions nd thats another 30%)
Mechanics, I know some of it from work through the last year so ill just hope for the best on that.
As for light sound and heat I dont know. Dont think i have the time to know them that well now but ill try my best.
Q5 is general knowledge of the course, easy questions but hard to study for due to the broad nature of the course.

Einstein's stuff is tipped due to this 100year thing ill av a look over that aswell.
Anybody got any experiment tips or any other tips for what might come up?

Socrates

the experiment with the pendulum is widely tipped. and some experiment involving the trolleys on a runway, momentum acceleration etc. is expected. or so im told!

Waltons

I wouldn't be surprised if Snell's Law or measuring the refractive index of a liquid came up. I'd be inclined to go with the mechanics experiments mentioned above too. Most likely Section A will have stuff that hasn't been up before since it's such a new course. Apparently Electromagnetic induction always comes up in some form in question 12 too.

D-Generate

Pendulum won't come up.

Joules Law
F proportional to a
Snells Law
Speed of sound in air

My four guesses. Two graphs there aswell.

Waltons

Why do you think the pendulum won't come up?

stevoxbx

The measuring of gravity by the pendulum is tipped.
My guess is

Calculation of G by Pendulum
Snells Law
Speed of sound in air
1 of the specific latent heat ones
or else a mechanics experiment.

OTliddy

Whoa hold on a minute-is the speed of sound in air even on our course? In my physics book(Real World Physics), it doesn't say "sound 2" or "sound 3" or whatever. Also could two mechanics questions come up?

stevoxbx

Measurment of velocity of sound with resonance tube is on the course. Yes 2 mechanics could come up, Q6 for definate, then the option question 12.

Africa

Any ideas on what kinda q's could come upo in each of the little questions? Eveyone is so worried bout the experiments and the option that the others are being overlooked!!!

JackKelly

I have two questions from the mock that need answering.

Q1)Gas Molucules each of mass 7.8X10^-26Kg strike a flat surface. The average speed of the molecules perpendicular to the surface is 600ms-1 both before and after they strike it.Find:

1)the change in momentum of on of the moecules as a result of the collision

2)the number of molecules which collide with one square centimeter every second if the force on a square cenitmeter is 10N

3)the pressure produced on the surface due to the molecular collisions.

seriously.wtf?

Q2) A string fixed at both ends has a mass per unit length of 7.8X10-4kgm-1. The string vibrates at its natural frequency of 440Hz and a wavelength of 65Cm.Find:

1)the length of the string

2) the Tension of the string.

What i don't get in this one, is if it is vibrating at natural frequency, is that then the 1st harmonic? Becuase than the length is wavelength/2

any help is appreciated

*Angel*

TimAy wrote:

Q2) A string fixed at both ends has a mass per unit length of 7.8X10-4kgm-1. The string vibrates at its natural frequency of 440Hz and a wavelength of 65Cm.Find:

1)the length of the string

2) the Tension of the string.

Yes the length is half the wavelength

You can calculate the tension from the formula f = (T^1/2)/2l(mass per unit length)^1/2

JackKelly

*Angel* wrote:

Yes the length is half the wavelength

You can calculate the tension from the formula f = (T^1/2)/2l(mass per unit length)^1/2

cool, thats what i thought. Thank you

*Angel*

As for the other one I'm clueless, are you sure you're not given any other info especially for the first part.

sixdraw

ah i got that question in my mocks aswell, got full marks mind you.
the change in momentum is twice the original momentum.cause momentum is a vector quantity so
change in momentum = initial momentum - (- initial momentum)
as speed and mass are the same before and after collision

*Angel*

sixdraw wrote:

ah i got that question in my mocks aswell, got full marks mind you.
the change in momentum is twice the original momentum.cause momentum is a vector quantity so
change in momentum = initial momentum - (- initial momentum)
as speed and mass are the same before and after collision

Handy to know

Errant11235

"is 600ms-1 both before and after they strike it"

There is no change in momentum, since there velocity does not change.
I don't think the 10N is of any use, f=ma, a=0 etc...
Are you sure you're not leaving something out?

sixdraw

there is change in momentum as its a vector quantity. the directions are opposite , before and after

sixdraw

as with the 10N, you calculate the acceleration of each particle per second. using v = u + at. t = 1 in this case . you can do initial velocity - new velocity over time taken.
put that into f=ma. this gives you the force produced by each particle. divide 10N by this force and you get the number of molecules

Africa

Experiments wise, in 2004:
Freefall G
Funda Freq of F with length
Nichrome wire
Wavelength of Monocromatic light
2003:
Boyles Law
SLH of vaporisation of water
Focal length of converging lens
Joules Law
2002: Law of Equilibrium
SLH of Ice
Funda Freq of F with tension
variation of current I with Pot V.

Anyway. I say for this year learn the following:
Ohms Law (variation of resistence of thermistor/Metal with temp) yes thats 2 different experiements very the same...easy enough.
Calibration Curve of Thermometer using merc as standard
SHC of water
Sound speed in Air
Length and period of Pendulum, find G.
Measurement of Velocity and Acceleration
Newtons Second law, A proportional to F
Schnells Law
Focal length of lens's.

thats about ten, i say that at least 3 of those will come up.. If not...i will eat my teacher.

Errant11235

"600ms-1 both before and after they strike it"

Initial velocity=600ms/s
Final Velocity =600ms/s

v=u+at
0=at!!!

I must be completely misreading the question, if each molecule is moving at 600ms, hits off something and then continues travelling at 600ms it has not lost any momentum (in the sense p=mV.)

If I'm way off the mark please explain! This is going to piss me off untill I get the right answer!

xinran

its initial velocity is +600ms-1, its final velocity is -600ms-1 because its now going the opposite direction.
then the change in P is (600m-(-600m) and this will give you the actual change in momentum.

OTliddy

TimAy wrote:

Q1)Gas Molucules each of mass 7.8X10^-26Kg strike a flat surface. The average speed of the molecules perpendicular to the surface is 600ms-1 both before and after they strike it.Find:

1)the change in momentum of on of the moecules as a result of the collision

2)the number of molecules which collide with one square centimeter every second if the force on a square cenitmeter is 10N

3)the pressure produced on the surface due to the molecular collisions.

Did anyone else get these answers?-1)9.36x10^-23
2)1.068376x10^23
3)1000N

sixdraw

ya that looks right, except 3) is 3kpa not N.