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# Unit 4 Physics Edexcel A2 and Edexcel IAL Watch

1. (Original post by Dr.strange12)
Hey can anyone help with question 5 and question 15. c)

http://qualifications.pearson.com/co...e_20100128.pdf
For question 5 you can see that as side QS is perpendicular to the side QP, then the side QS must also be perpendicular to the plane containing the magnetic field so the value for the force is at a maximum. You can then use force=BIL and then multiply that by 50.

The magnetic field must be going into the page in 15c by Fleming's Left Hand Rule. It's a positively charged particle so the current is moving up through the plate, the force acts centripetally towards the left hand side of the page therefore the field must be in.
2. Why is the answer B? I thought particles gained mass as they approached the speed of light.
3. (Original post by target21859)
Why is the answer B? I thought particles gained mass as they approached the speed of light.
Yes particles do gain mass as they move close to the speed of light. The positron mass given in the question is larger than a positron's rest mass therefore the answer is B
4. (Original post by Mowerharvey)
Yes particles do gain mass as they move close to the speed of light. The positron mass given in the question is larger than a positron's rest mass therefore the answer is B
Forget I asked I was thinking of the mass of a proton. I need sleep haha
5. Hi. Can someone please explain and show this to me? This is June'12, Q-18)c)
6. (Original post by target21859)
Forget I asked I was thinking of the mass of a proton. I need sleep haha
7. (Original post by target21859)
Why is the answer B? I thought particles gained mass as they approached the speed of light.
I thought of it as .. mass of electron/positron = 9.11x10^-31 kg emphasis just on the power indice ( ^-31) whereas the question context says (^-28) so therefore the mass of the positron has increased, which only occurs during relativistic effects such as travelling close to speed of light.
8. I don't understand this question at all...or physics.
9. (Original post by target21859)
I don't understand this question at all...or physics.
At T the current passes through the coil which makes it rotate, because it is in a magnetic field. As it rotates, there is a change in flux linkage and therefore an emf is induced. Due to lenzs law, the direction of the emf will oppose the change that caused it, and in this case that is the motion of the coil. Therefore the current decreases over time, and that is why D is the answer
10. (Original post by Mowerharvey)
Is physics unit 4 anyone else's last exam?
Unit 5 physics?
11. (Original post by ayvaak)
Unit 5 physics?
Oh yeah I forgot about unit 5, I'm retaking so I'm only doing unit 4.
12. (Original post by Mowerharvey)
Oh yeah I forgot about unit 5, I'm retaking so I'm only doing unit 4.
#
have you retaken any other exams?
13. (Original post by ayvaak)
#
have you retaken any other exams?
Yes, Edexcel History and Aqa Maths core 3 and 4. Needed to get AAB last year but only got BBC
14. (Original post by Mowerharvey)
Yes, Edexcel History and Aqa Maths core 3 and 4. Needed to get AAB last year but only got BBC

The Unit 4 paper last year was deadly for most people in the year in my school. A grade students were getting Ds and Cs.

But good luck this year. Where are you hoping to go this year uni wise? If you dont mind me asking?
15. (Original post by ayvaak)
The Unit 4 paper last year was deadly for most people in the year in my school. A grade students were getting Ds and Cs.

But good luck this year. Where are you hoping to go this year uni wise? If you dont mind me asking?
Yeah I got As in all the other physics papers but a C in unit 4 brought my grade down to 4 ums off of an A.

Thank you . Last year i wanted to go to Exeter, but this year I decided to go for UEA because I like Norfolk.

What university are you thinking of going to?
16. (Original post by Mowerharvey)
Yeah I got As in all the other physics papers but a C in unit 4 brought my grade down to 4 ums off of an A.

Thank you . Last year i wanted to go to Exeter, but this year I decided to go for UEA because I like Norfolk.

What university are you thinking of going to?

Hopefully Manchester for Engineering
17. (Original post by ayvaak)
Hopefully Manchester for Engineering
Nice, hope you get there
18. (Original post by Mowerharvey)
At T the current passes through the coil which makes it rotate, because it is in a magnetic field. As it rotates, there is a change in flux linkage and therefore an emf is induced. Due to lenzs law, the direction of the emf will oppose the change that caused it, and in this case that is the motion of the coil. Therefore the current decreases over time, and that is why D is the answer
Why can't it be B?
19. (Original post by Mowerharvey)
Nice, hope you get there
Yeah me too. Are you thinking of studying physics next year?

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20. (Original post by target21859)
Why can't it be B?
Eventually the current reaches a steady state, which will be before the current equals 0.

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