G484: OCR Physics A Unit 4 - 11th June 2014

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Time constraints on this exam are horrendous. Had literally about 1 minute to check through.

Not helped by that long winded Specific Heat Capacity question (by the way did everyone just use the normal immersion heater method for this? Just because it said 'small bottle' so I assume that you couldn't do that but I couldn't think about any other way of doing it. Would maybe say use a Bunsen but how would you find the energy used?).

Paper wasn't too bad (no horrible questions about calculating gravitational forces between planets, S.H.M was better than usual, etc.) but it's not helped by the time restraints which massively improve the scope for losing marks through silly errors.

You had to use an electrical heater. You can track voltage, current and time so that can give you energy.

Reply 101

Stakesby

Original post by Teraad

The only slightly tricky part was with the acceleration against displacement graph. Many people came out the exam saying they read off the maximum acceleration from the graph, however you couldn't do that and instead you had to work out the gradient to find the frequency.

to for out frequency i picked a point and used a=-(2*pi*f)x

gradient of a velocity displacement graph would give frequency

(edited 9 years ago)

Reply 102

Kits

Original post by Stakesby

to for out frequency i picked a point and used a=-(2*pi*f)x

Yep

Reply 103

cuckoo99

Original post by Stakesby

to for out frequency i picked a point and used a=-(2*pi*f)x

gradient of a velocity displacement graph would give frequency

a=-(2pi*f)^2 x you mean

i did the same method :smile:

Reply 104

ylli122

Original post by Kits

Yep

ω^2 surely...
Its the second differential..

Reply 105

Stakesby

Original post by Kits

Yep

what answer did you get?

Reply 106

audi_turbo

Original post by Stakesby

what answer did you get?

I got 5.6Hz or something

Yep

Original post by ibra456

For the plane going around the horizontal circle, what did you guys get?

Posted from TSR Mobile

i did Fsin35=mv^2 / r

r= mv^2 / fsin35

cant remember my value for r

Reply 109

username964430

Thought it was a rather standard paper, for the ratio, my thing simplified to 0.35(Temperature of sea/temperature at high altitude), or something like that
PV = NKT, when dividing, v and k cancels out etc...

Reply 110

Dr.Monstaa

What did people write for the 3 assumptions and question after that?

Reply 111

mb07

Original post by Dr.Monstaa

What did people write for the 3 assumptions and question after that?

gravitational force negligible, volume of molecules negligible compared to volume of container, all collisions between molecules, and between molecules and wall elastic

molecules elastically collide with walls, and each other. when collisions occur, there is a momentum change. force is proportional to rate of change of momentum. pressure = force/area.

decent paper, some awkward questions. i reckon 43 for A, 47 for A*, 51 being 100%.

Reply 112

username964430

Original post by Dr.Monstaa

What did people write for the 3 assumptions and question after that?

Large number of particles in rapid random motion,
Volume of particles negligible compared to volume of container
Collisions between particles and wall perfectly elastic
And so many more

Particle hits wall, change in momentum = 2mv, force proportional to change in momentum, pressure proportional to force, a large number of particles = noticeable pressure exerted, or something along those lines