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AQA Physics PHYA4 - Thursday 11th June 2015 [Exam Discussion Thread]

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Hey guys does anyone know how to calculate the time period for this:
January 2011

The correct answer is B but my calculations can never get that answer.
Apparently we are supposed to use ω²r = 9.81

Thanks :smile:

mw^2r = GMm/r^2

rearranges to

w = (GM/r^3)^1/2

You get the answer in seconds, so divide it by 3600 and it should be 1.4 hours.

Make sure you cube the radius

Reply 3701

saad97

Original post by Dante991

yeah me too, 19 was just like what

Tbh I'm like that with most of these mc questions and it's not good when we're just over 12 hours away from the exam! :frown:

Could you help me with 20 and 21 please if you got them? Thanks.

Reply 3702

frankiejayx

Anyone mind explaining Q15 of multiple choice 2014?

Reply 3703

MsFahima

Original post by saad97

Tbh I'm like that with most of these mc questions and it's not good when we're just over 12 hours away from the exam! :frown:

Could you help me with 20 and 21 please if you got them? Thanks.

Tell me about it :redface:

Which paper are those questions from?

Reply 3704

DanielWall96

Original post by frankiejayx

Anyone mind explaining Q15 of multiple choice 2014?

Post a link to the question pls

Reply 3705

username1571649

Original post by saad97

Tbh I'm like that with most of these mc questions and it's not good when we're just over 12 hours away from the exam! :frown:

Could you help me with 20 and 21 please if you got them? Thanks.

I'm looking for someone to show me how to do them too, absoulte killer paper

Reply 3706

Adangu

Original post by DanielWall96

Post a link to the question pls

http://filestore.aqa.org.uk/subjects/AQA-PHYA41-QP-JUN14.PDF

Reply 3707

DanielWall96

Original post by Dante991

I'm looking for someone to show me how to do them too, absoulte killer paper

I'll try help link me the questions

Reply 3708

saad97

Original post by Dante991

I'm looking for someone to show me how to do them too, absoulte killer paper

I hope ours is much more straight forward but I doubt it considering how my exam's have gone so far this year, I've just lost all motivation to revise -_-

Reply 3709

Zeus579

I'm going to fail ...

Reply 3710

JaySP

Original post by C-king

BUMP

Reply 3711

saad97

Original post by DanielWall96

I'll try help link me the questions

http://filestore.aqa.org.uk/subjects/AQA-PHYA41-QP-JUN14.PDF

19, 20 & 21 please, thanks.

Reply 3712

samlyon

Original post by samlyon

http://www.tomred.org/uploads/7/7/8/3/778329/physics_qp_u4b_specimen.pdf
http://www.tomred.org/uploads/7/7/8/3/778329/physics_ms_u4_specimen.pdf

Can anyone explain 2b please, how do you know what the phase difference is from the frequency?

Anyone? I'm just confusing myself

Reply 3713

DanielWall96

Original post by Adangu

http://filestore.aqa.org.uk/subjects/AQA-PHYA41-QP-JUN14.PDF

so each charge is providing half the potential
25/2 = 12.5

The potential from P is doubled as the distance is halved so = 25
The potential from Q is decreased by 1/1.5 so becomes 8.333333333
25 + 8.3333333= 33.3

C

Reply 3714

jh52

Original post by QueNNch

Hey guys does anyone know how to calculate the time period for this:
January 2011

The correct answer is B but my calculations can never get that answer.
Apparently we are supposed to use ω²r = 9.81

Thanks :smile:

If the object is to appear weightless, then the centripetal force needs to be equal to the weight, so that the resultant force is zero. Therefore mg = mw²r. The masses cancel each other out, so that gives you w²r = 9.81. Then substitute 2pi/T for w and rearrange to get the answer. :smile:

Reply 3715