You are Here: Home >< Physics

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

1. (Original post by sykik)
Can anyone explain why racing tracks are bunked in terms of centripetal force.
It reduces the frictional force on the tyres as the horizontal component of weight will provide some of the centripetal force keeping the car on the track. If the ground was flat there would be no horizontal component of weight. .

This means that you can go around a bend on a banked track quicker than you can when its flat

Posted from TSR Mobile
2. (Original post by _Caz_)
It reduces the frictional force on the tyres as the horizontal component of weight will provide some of the centripetal force keeping the car on the track. If the ground was flat there would be no horizontal component of weight. .

This means that you can go around a bend on a banked track quicker than you can when its flat

Posted from TSR Mobile
When the ground is flat how does frictional force provide centripetal force?
3. (Original post by sykik)
When the ground is flat how does frictional force provide centripetal force?
Frictional force on the tyres keeping the car in a circular path is the centripetal force

Posted from TSR Mobile
4. (Original post by Mehrdad jafari)
Frictional force on the tyres keeping the car in a circular path is the centripetal force

Posted from TSR Mobile
But isn't centripetal force towards the centre? I donno i am getting confused like how can friction provide centripetal force?
5. (Original post by sykik)
But isn't centripetal force towards the centre? I donno i am getting confused like how can friction provide centripetal force?
No, you're not confused, your question is reasonable. The centripetal force is the force required to keep a body in a circular motion, whether that be the circular motion of the earth around the sun or a car turning a roundabout. A car cannot turn around a circle if there is no friction between the tyres and the road because bodies have the "tendency" to move in a straight line. So a car going around in a circle will need a force keeping it in its path and that force is the frictional force. Of course this force is acting towards the centre of the circle because that's how the frictional force is able to keep the car in a circular path.
In fact if there was no frictional force between the tyres and the road (assuming it had some jet engine to power)and the car was attached by a string to the centre of the circle then the string would do the same job as the friction between the tyres.
Is that quite clear?

Posted from TSR Mobile
6. Thanks it makes a lot more sense now.
7. (Original post by sykik)
Thanks it makes a lot more sense now.
No worries. I'm happy it helped

Posted from TSR Mobile
8. Guys, it's very awkward but last night i dreamt that i was doing phys5 paper and the six marker was the proof of the kinetic theory of gas equation. My mind may be subjective this time due to the lots of comments it has seen on here lol

Posted from TSR Mobile
9. (Original post by Mehrdad jafari)
Guys, it's very awkward but last night i dreamt that i was doing phys5 paper and the six marker was the proof of the kinetic theory of gas equation. My mind may be subjective this time due to the lots of comments it has seen on here lol

Posted from TSR Mobile
I thought this too! But surely that would be to easy for a 6 marker ??

Posted from TSR Mobile
10. (Original post by gcsestuff)
I thought this too! But surely that would be to easy for a 6 marker ??

Posted from TSR Mobile
But they've never asked this before, and all of the nuclear stufff has been exhausted. Plus nothing on gases for a while (unless they put in a question about thermal)
11. So it's either a thermal experiment, or the kinetic theory
12. (Original post by gcsestuff)
I thought this too! But surely that would be to easy for a 6 marker ??

Posted from TSR Mobile
Well, not if it it was worth less than six marks. And also the derivation of the equation in the textbook seems quite wrong even though the final equations seems right.

Posted from TSR Mobile
13. (Original post by AR_95)
So it's either a thermal experiment, or the kinetic theory
What thermal experiment could it be?
14. Could someone help me with june 2013 question 1 part c? thanks a lot
15. Does anyone know of any solutions to the multiple choice questions?

Posted from TSR Mobile

16. Hi can anyone explain what should the angle be between. I came across a multiple choice question where they had given us a wrong angle and we had o workout the right one but i don't understand the angle should be between? Thanks
17. Just read that emf is always induced, but current only if the circuit is complete. Can someone explain this a bit? So if the coil was not all the way round, and had a gap, and you drop a magnet through it, will it take longer than if there is no coil?

Posted from TSR Mobile
18. Also, can somebody explain alternators from scratch? Including why it's so important we use AC, just everything that's going on there!

Posted from TSR Mobile
19. Hi I get why EMF is 20 but i don't get how you workout frequency ?
20. (Original post by chughes17)
Just read that emf is always induced, but current only if the circuit is complete. Can someone explain this a bit? So if the coil was not all the way round, and had a gap, and you drop a magnet through it, will it take longer than if there is no coil?

Posted from TSR Mobile
The reason emf is induced in conductors is that charged particles move when in a magnetic field. emf is the potential difference - so the difference in charges - which you'll get in an incomplete circuit because charge will build up at one end due to movement of electrons. In a complete circuit, the electrons continue moving, so you get a flow of charge - a current.

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: February 22, 2016
Today on TSR

### Exam Jam 2018

Join thousands of students this half term

### Solo - A Star Wars Story

Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE