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AQA Physics A Unit 4- 11 June 2014

Reply 580

OliverG

2

Original post by Islam2014

Dont understand why it would be D

Using Ek = 1/2mv^2

Double mass, double energy. Simple enough.
Vmax = 2pifA. So double f, double Vmax

velocity is squared, and 2^2 = 4

So E*4*2 = 8E

So D.

Reply 581

OliverG

2

Original post by Islam2014

Thank you really appreciate the help
Lol yeh he said something about them changing too often so theres no point in buying them :s-smilie:

No problem. We use the Nelson Thornes ones. Admittedly the fact that the book in its current form is out and exclusively endorsed by AQA is an utter, UTTER disgrace though. The data sheet is wrong in at least 2 places, and several of the exam style questions are incorrect and give invalid answers. Oh yes, and it has a couple of chapters of things that aren't on the syllabus and has LOADS AND LOADS AND LOADS of needless waffle. The book should be less than 2/3 the size it currently is.

Reply 582

user1-4

1

hey how do you work out the acceleration at any moment using a force againt time graph?

Reply 583

user1-4

1

and this question

A tennis ball of mass 5.0 × 10−2
kg moves at 12 m s−1 perpendicularly towards a tennis
racket. After being hit by the racket the ball rebounds along the same line at 18 m s−1.
What is the change in the momentum of the ball?
A 0.30 N s directed towards the racket
B 0.30 N s directed away from the racket
C 1.5 N s directed towards the racket
D 1.5 N s directed away from the racket

the answer is D but i am sure its C?

Reply 584

OliverG

2

Original post by user1-4

and this question

A tennis ball of mass 5.0 × 10−2
kg moves at 12 m s−1 perpendicularly towards a tennis
racket. After being hit by the racket the ball rebounds along the same line at 18 m s−1.
What is the change in the momentum of the ball?
A 0.30 N s directed towards the racket
B 0.30 N s directed away from the racket
C 1.5 N s directed towards the racket
D 1.5 N s directed away from the racket

the answer is D but i am sure its C?

It's change in momentum. So Final momentum - Initial momentum

It is moving towards the racket, and by the end it is moving away from the racket. The rate of change of this momentum is equal to force, so if the change in momentum is towards the racket it will still be going in its initial direction (i.e. in the direction that was initially towards the racket). And common sense dictates that if the ball rebounds, it hasn't gone through the racket and kept going, so it must have changed direction, so the change of momentum is away from the racket.

Reply 585

spiruel

Original post by user1-4

and this question

A tennis ball of mass 5.0 × 10−2
kg moves at 12 m s−1 perpendicularly towards a tennis
racket. After being hit by the racket the ball rebounds along the same line at 18 m s−1.
What is the change in the momentum of the ball?
A 0.30 N s directed towards the racket
B 0.30 N s directed away from the racket
C 1.5 N s directed towards the racket
D 1.5 N s directed away from the racket

the answer is D but i am sure its C?

Rebounds along the same line, so in other words the velocity is in the opposite direction.
Change in momentum is away from the racket.

Reply 586

spiruel

Original post by user1-4

hey how do you work out the acceleration at any moment using a force againt time graph?

Find force at that specific point, divide by mass.

(edited 9 years ago)

Reply 587

nilojan11341

anyone got their unit 5 notes, happy to share? :smile:

just want to compare them to mine
also anyone have notes on turning points?

Reply 588

lebron_23

2

The wording confuses me a little.

The working here confuses me a little.

I'd be grateful if someone could just run me through it.

Thanks!

Screen shot 2014-06-10 at 14.45.10.png18.8KB

Reply 589

Jimmy20002012

4

What are the phase differences we need to know about driven dispalcements?

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Reply 590

Student95!

1

Could anyone explain how you work out resultant electric field strengths and how to find the distance from a charge that they are them to be no resultant E, thanks

Reply 591

kashagupta

6

How do you know when to use Fleming's right hand rule? Is that even on the spec?

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Reply 592

Roostertooster

Hi all, cut a long story short I'm working this evening and am planning to right a few condense notes n my palm so every time I stack a shelf I re read to kinda re enforce, I struggle with induction and transformers, question is - can anyone give me some condensed lines of the key points for these sections,
Thanks

Reply 593

nilojan11341

how should you answer the 6 markers to make sure you get all the marks? any tactics? ive looked at the mark scheme already.

Reply 594

EllBailz

If you 2x the charge stored on a capacitor does the energy stored 4x? E=Q^2/2C ??

Reply 595

sheepshap

8

Did anyone else find june 2013 really challenging?!?!?!?!?!?!?!

Reply 596

dudesamld

Original post by nilojan11341

how should you answer the 6 markers to make sure you get all the marks? any tactics? ive looked at the mark scheme already.

I think a good plan is key, and draw diagrams to help explain! Treat the examiner as a child who needs to know every step, that way you avoid being jumpy.

Reply 597

dudesamld

Original post by sheepshap

Did anyone else find june 2013 really challenging?!?!?!?!?!?!?!

I thought the 6 marker was particularly difficult. Grade boundaries for this year was actually one or two higher than previous years with 53/75 for an A.

Reply 598

dudesamld

Original post by EllBailz

If you 2x the charge stored on a capacitor does the energy stored 4x? E=Q^2/2C ??

Yes. Perfect!

Reply 599

Surf

15

Original post by sheepshap

Did anyone else find june 2013 really challenging?!?!?!?!?!?!?!

What part did you find hard? I did that one just this morning - as I saved it..... but I found it a good paper compared to the jan 12 paper..... and the 6 marker was fairly easy.

Maybe if you say what you found hard then people can help?

AQA Physics A Unit 4- 11 June 2014

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