Official OCR A2 G484 June 2016 [Module 1] [90UMS]

part i) you need to do is divide 24 hours by the time period to get 14.2 orbits in 24 hours

part ii) we need to find the number of orbits it would take to photograph. So if we find the circumference (6400 x 10^3 x 2pi) and then divide that by 3000 x 10^3 m, we get that it would take 13.4 orbits to photograph the whole of the surface. In part i, we showed that the satellite makes 14.2 orbits in 24 hours so if we compare 13.4 with this figure we can see that the satellite will be able to photograph the whole of the surface in 24 hours

But in the mark scheme they divide 13.4 by 2 whys that

Reply 101

Aph

22

Original post by Revision King98

But in the mark scheme they divide 13.4 by 2 whys that

Assuming that 13.4 is the circumference of earth? And that's because each orbit will cross the equator twice.

Reply 102

ukcolBehT

2

June 14 Q 3b ii)
Why does the KE drop to 1/4 if height from which is dropped is halved?Wouldn't it also be halved?

Reply 103

Jammydodgerdenny

1

Original post by ukcolBehT

June 14 Q 3b ii)
Why does the KE drop to 1/4 if height from which is dropped is halved?Wouldn't it also be halved?

Vmax=(2πf)A.

Therefore if the amplitude is halved Vmax is also halved. KE=1/2mv^2 . So if Vmax is half KE is (1/2)^2, so 1/4 the original.

Reply 104

TheFarmerLad

22

Do we need G485 content for this exam?

Reply 105

only1hman

Good luck every one, lets get these A's!

Reply 106

msulli

2

Any one have a copy of the 2015 paper?

Never mind found it

Here is a link if anyone needs it

https://drive.google.com/folderview?id=0B989KkRnVfa7NW50NXdzTllLc1U&usp=drive_web

(edited 7 years ago)

Reply 107

_MAT_

2

Original post by TheFarmerLad

Do we need G485 content for this exam?

It wouldn't surprise me if there were questions of G485

Reply 108

Jold

1

Bit confused on a question from the June 2013 paper:

" Q3 (a) An object is oscillating with simple harmonic motion. Place a tick in the box against each statement that applies to the acceleration of the object:

The acceleration...

Is in the opposite direction to the displacement.

Is directly proportional to the amplitude squared.

Increases as the displacement decreases.

Increases as the speed of the object decreases. "

I ticked statements 1 and 3, but the mark scheme says its 1 and 4, and Im not sure why. Someone help!!!

Reply 109

JxxxjoexxxJ

1

Original post by Jold

Bit confused on a question from the June 2013 paper:

" Q3 (a) An object is oscillating with simple harmonic motion. Place a tick in the box against each statement that applies to the acceleration of the object:

The acceleration...

Is in the opposite direction to the displacement.

Is directly proportional to the amplitude squared.

Increases as the displacement decreases.

Increases as the speed of the object decreases. "

I ticked statements 1 and 3, but the mark scheme says its 1 and 4, and Im not sure why. Someone help!!!

3 is incorrect. Amplitude is proportional to negative displacement i.e a=-(2pif)^2X note the MINUS sign. So as displacement increases acceleration increases but in the opposite direction, otherwise it would never return to the midpoint. Therefore acceleration increases as displacement increases. NOT acceleration increases as displacement decreases which is the quote from the question.

4 is correct as the speed of the object decreased it is getting closer to the end point, so the displacement is bigger so the acceleration is bigger. when velocity is max, it is at equilibrium and hence acceleration is minimum. Therefore as speed decreases acceleration increases.

(edited 7 years ago)

Reply 110

PotAuFeu

6

Original post by TheFarmerLad

Do we need G485 content for this exam?

If there is, I doubt it would be anything that you haven't remembered off by heart already. They'd rather test your G484 knowledge than your G485 knowledge.

Reply 111

89911998a

1

1) What factors affect damping? i.e. mass, amplitude, frequency, acceleration.

2) How would you describe in detail how to conduct an experiment to illustrate Brownian motion? (5/6 marker)

3) Why is the sum of the kinetic energies of each of the different types of gas molecules (e.g. oxygen, hydrogen, etc) at a given temperature equal to each other (regardless of differences in molar mass, etc)

4) What factors in each oscillating system affect time period/frequency?

5) When exactly are you supposed to use a = v^2/r, and when does a = g? Does it apply to circular motion, impulse and momentum, gravitational fields?

Reply 112

giorgias

can someone please help me with question 1 a) ii) june 2015

Reply 113

kingLAWZA

13

Can someone help me with these 2 questions please, the part ii for the first

i'm confused why the rate is multiplied by what it is in the mark scheme

https://gyazo.com/9f54958ea5e0978082c727430744660f

https://gyazo.com/bff030e25600591af2e0082589b5157d

Reply 114

Revision King98

1

Original post by 89911998a

1) What factors affect damping? i.e. mass, amplitude, frequency, acceleration.

2) How would you describe in detail how to conduct an experiment to illustrate Brownian motion? (5/6 marker)

3) Why is the sum of the kinetic energies of each of the different types of gas molecules (e.g. oxygen, hydrogen, etc) at a given temperature equal to each other (regardless of differences in molar mass, etc)

4) What factors in each oscillating system affect time period/frequency?

5) When exactly are you supposed to use a = v^2/r, and when does a = g? Does it apply to circular motion, impulse and momentum, gravitational fields?

More frictional force will mean a shorter time to reduce the amplitude

2) I would just memorise from
Book
3) as temperature only effects KE, so if molar mass is different, as long as you have the same mass the KEs will be same, but that means for the same KE in oxygen and hydrogen masses must be different?

4) for simple harmonic motion the frequency and period are independent of amplitude
So to change period and frequency probably add a heavier mass (not too sure)

Reply 115

Artmanlikesart

1

Original post by hallo.C

part i) you need to do is divide 24 hours by the time period to get 14.2 orbits in 24 hours

part ii) we need to find the number of orbits it would take to photograph. So if we find the circumference (6400 x 10^3 x 2pi) and then divide that by 3000 x 10^3 m, we get that it would take 13.4 orbits to photograph the whole of the surface. In part i, we showed that the satellite makes 14.2 orbits in 24 hours so if we compare 13.4 with this figure we can see that the satellite will be able to photograph the whole of the surface in 24 hours

Can you explain why my answer is incorrect?
Surface area of Earth = 4pi/3(6.4 x 10^5)^3 = 1.56 x 10^21 m^2

Area captured by camera = 14(orbits) x 2pi x (6.4 x 10^5) x (3 x 10^3) = 1.9 x 10^15 m^2
Surely the satellite can't capture the entire surface then?

I

Reply 116

89911998a

1

Original post by Revision King98

More frictional force will mean a shorter time to reduce the amplitude

2) I would just memorise from
Book
3) as temperature only effects KE, so if molar mass is different, as long as you have the same mass the KEs will be same, but that means for the same KE in oxygen and hydrogen masses must be different?

4) for simple harmonic motion the frequency and period are independent of amplitude
So to change period and frequency probably add a heavier mass (not too sure)

Thank you. So for 3) since hydrogen and oxygen have different molar masses, for KE to be the same the number of moles present of each must be different. This will make the masses equal each other.

Reply 117

Tajwar786

2

Does anyone have ocr mark scheme for these two 4/5 markers:

1) explain how the principle of conserv. Of momentum is a natural consequence of newtons laws
2) explain briefly how the illusion of centrifugal force arises

Reply 118

PotAuFeu

6

Original post by 89911998a

1) What factors affect damping? i.e. mass, amplitude, frequency, acceleration.

2) How would you describe in detail how to conduct an experiment to illustrate Brownian motion? (5/6 marker)

3) Why is the sum of the kinetic energies of each of the different types of gas molecules (e.g. oxygen, hydrogen, etc) at a given temperature equal to each other (regardless of differences in molar mass, etc)

4) What factors in each oscillating system affect time period/frequency?

5) When exactly are you supposed to use a = v^2/r, and when does a = g? Does it apply to circular motion, impulse and momentum, gravitational fields?

To add onto what Revision King said...

2) Trap smoke in smoke cell
Cover top of cell with cover slip
Focus light onto cell using glass rod and bulb
Focus microscope on smoke particles in smoke cell

3) E=kT, E is kinetic energy, k is Boltzman constant, T is absolute temperature

4) I'm not sure if this is technically in the specification but you can look at the AQA formula sheet to see what affects period. i.e. for SHM on a spring, period is proportional to root of mass (but NOT length). For SHM on a string, period is proportional to root of length of string (but NOT mass).

5) Used in circular motion.
Not sure if this exactly what you want but for weightlessness for motion in a vertical motion, a=g at the top of the circle. Hence weight provides the centripetal force so no contact force between you and the vehicle so you feel "weightless".

Reply 119

Danimtz

1

Original post by kingLAWZA

Can someone help me with these 2 questions please, the part ii for the firsti'm confused why the rate is multiplied by what it is in the mark schemehttps://gyazo.com/9f54958ea5e0978082c727430744660f https://gyazo.com/bff030e25600591af2e0082589b5157d

For part ii on the first one, you calculate the force of the engine in 1 second (F = rate of change of momentum), so the mass of the all the xenon ions ejected in 1 second x their initial speed all over the time(1 second) . Then using Newton's third law you know the force on the spaceship and you can use F=ma to find acceleration.

For the laser question, you are given the energy of a single photon and the rate of emission of the photons. (Joules and "per second" --> Joules per second)
Then using he E=mc x change in temperature, you can find out the energy necessary to heat the titanium.

Joules/Joules per second = time

(edited 7 years ago)

Official OCR A2 G484 June 2016 [Module 1] [90UMS]

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