OCR B Physics G494 June 11th 2014 Unit 4

Reply 80

VARRRDAQ

3

Anyone get 4.6 x 10^19 m for the distance of the galaxy away from Earth?

Reply 81

RATKING

Original post by VARRRDAQ

I think so anyway - what did you put as your second point?

Lol nothing I just kkinda repeated myself I think. So 1 mark. I said like max amplitude due to resonance will be lower as damping causes amplitude to be lower....

Posted from TSR Mobile

Reply 82

StuffItThat'llDo

Original post by RATKING

Ahh I didn't mention energy. That was probably the second mark.

Posted from TSR Mobile

got me too :P

Reply 83

Dan1300

Yeah that rings a bell. Did you work out the change in gravitational potential energy and equate that to the gain in kinetic energy?

Reply 84

Fillly

Original post by Expert #7451

I got something a lot higher than that. I had to assume that if KE didn't change, then mass had to change to maintain KE and the inevitably different velocity.

I got something like the asteroid's mass was reduced to 100kg, and that when it got to the earth's orbit it would have reached a velocity of approximately 42000 m/s.

Hmm that's a good point about the mass. I calculated the total energy of the Asteroid with its initial KE and PE and then did some wierd manipulations using its new PE at earth's radius to somehow get 19200. :confused:

Reply 85

chi80

6

Original post by CrystalPlanet

Was it an an asteroid or comet? Because I got a high value for that question which is roughly the speed of a comet near Earth..

Edit: I remember it weighed 500kgs? That would be more like the weight of a comet; I got around 37000m/s. Anyone else?

i got something like that too.

Reply 86

StuffItThat'llDo

to be honest, it seems that people found it hard in general. we all know how many marks you can lose and still get a good mark. it's not like maths where it's generally 80% for an A. hope that reassures you guys, i got baffled on a few parts too, but have to concentrate on next exams now. g495 is the scary one xD

Reply 87

Lottiedottie

Original post by Fillly

Hmm that's a good point about the mass. I calculated the total energy of the Asteroid with its initial KE and PE and then did some wierd manipulations using its new PE at earth's radius to somehow get 19200. :confused:

yeah I alos got 1.9 X10^4, but realised it must have been wrong because it was the same as the initial speed if you checked back, so I think we may have both made the same mistake

Reply 88

CrystalPlanet

Original post by Expert #7451

I got something a lot higher than that. I had to assume that if KE didn't change, then mass had to change to maintain KE and the inevitably different velocity.

I got something like the asteroid's mass was reduced to 100kg, and that when it got to the earth's orbit it would have reached a velocity of approximately 42000 m/s.

How did the mass reduce?

Reply 89

username1385474

9

Original post by CrystalPlanet

Was it an an asteroid or comet? Because I got a high value for that question which is roughly the speed of a comet near Earth..

Edit: I remember it weighed 500kgs? That would be more like the weight of a comet; I got around 37000m/s. Anyone else?

I got something around that too.

Reply 90

ps321

2

Original post by chi80

i got something like that too.

Same here.

Reply 91

tom32

Original post by CrystalPlanet

Was it an an asteroid or comet? Because I got a high value for that question which is roughly the speed of a comet near Earth..

Edit: I remember it weighed 500kgs? That would be more like the weight of a comet; I got around 37000m/s. Anyone else?

Yeah I have the value 3.76X10^4 stored on my calculator

Reply 92

VARRRDAQ

3

Original post by CrystalPlanet

How did the mass reduce?

Yea pretty sure the mass doesn't change - the weight changes.

Reply 93

StuffItThat'llDo

Original post by Dan1300

Yeah that rings a bell. Did you work out the change in gravitational potential energy and equate that to the gain in kinetic energy?

personally i got stuck on that question and very quickly moved on :P

Reply 94

VARRRDAQ

3

For the Hubble's law what did people get?

Reply 95

rossmafudge

1

that was a tricky paper

Reply 96

Prinz655

Reactions to the exam?

Reply 97

Dan1300

Original post by VARRRDAQ

For the Hubble's law what did people get?

I can't remember the figure but you just do 1/the age of the universe to get the hubble constant, and then use v=H0d to work out d

Reply 98

ps321

2

For the asteroid question I didn't say explicitly that the gain in KE was equal to the loss of GPE. I got around 37700m/s which other people seem to have got. IF this is right, do you think I will get BOD (Benefit of Doubt) for not stating my assumption? You weren't asked to state assumptions.

Reply 99

CrystalPlanet

Original post by VARRRDAQ

Yea pretty sure the mass doesn't change - the weight changes.

But weight is to do with the force of attraction; the total energy is still conserved, so even if the weight is changes it is taken into account when you equate the total potential energy to the gravitational potential and kinetic energy per mass. That way velocity can be worked out. If I'm wrong correct me, I'd really like to know whether I got this question right haha. Considering it was 4 marks.

OCR B Physics G494 June 11th 2014 Unit 4

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you