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

Reply 4100

Fred Cantoni

2

Original post by Disney0702

How is the first question acceleration.
Is rate of change of momentum really acceleration?

No. It's force.

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Reply 4101

Disney0702

9

Original post by QueNNch

Well the motion is horizontal so weight is NOT included.

Vertical components and horizontal components are independent (we learned this is AS Unit 2)

Damn!

Reply 4102

DannySmith420

1

Original post by Will177

I think I just did mv^2/r = T because its horizontal and weight is verticle. Can't remember what value I got

I think thats wrong because the weight of particle is not taken into account. I did T - mg = mv^2/r

Reply 4103

Hexaneandheels

4

I put Weber Turns as the units...correct or?

Reply 4104

wat a wizard

13

Original post by Disney0702

How is the first question acceleration.
Is rate of change of momentum really acceleration?

Did you put weight?

Reply 4105

Fvthoms

2

Original post by Disney0702

Grade boundary predictions?

55 for A*
50 for A
etc...

Reply 4106

wat a wizard

13

Rate of change of momentum is Ns/s = N?

Reply 4107

Absent Agent

21

Original post by Disney0702

How is the first question acceleration.
Is rate of change of momentum really acceleration?

Yeah, thats how F=ma is derived

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Reply 4108

Sbarron

3

Original post by Humbers

It was rotated horizontally so weight is perpendicular to centripetal force therefore ignored

T = mv^2/r 0.25 x 8.6^2 / 1.5 = 12.3N

I put T = +F

Reply 4109

Fred Cantoni

2

Original post by DannySmith420

I think thats wrong because the weight of particle is not taken into account. I did T - mg = mv^2/r

It said assume string is horizontal though

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Reply 4110

QueNNch

3

Original post by Mehrdad jafari

Here are my answers. The ones I'm not sure with i have mentioned next to them.

I have failed to take the answer of one of the MC questions. Let me know if you found which one.
I would be very happy if you could correct the ones that are not right :smile:

ImageUploadedByStudent Room1434019809.052314.jpg

Thanks for putting them!

I think you question 17 is incorrect because the question asked for the number on electrons on the NEGATIVE plate ONLY. Therefore the answer is half of what you got. (something like 2.2 x 10^10)

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(edited 8 years ago)

Reply 4111

imyimy

3

Original post by fruity97

I got 15N at first for tension! But I remember changing it towards the end to 12N because I didn't include the weight I think? Stil not sure which is right but they said horizontal so I changed it

Yeah that's why I think it's wrong :/

Reply 4112

Will177

3

Original post by Mehrdad jafari

Here are my answers. The ones I'm not sure with i have mentioned next to them.

I have failed to take the answer of one of the MC questions. Let me know if you found which one.
I would be very happy if you could correct the ones that are not right :smile:

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Pretty sure 22 was 1/rt2 maybe you forgot to root each side?

Reply 4113

kevincarreira

6

Original post by Mehrdad jafari

Here are my answers. The ones I'm not sure with i have mentioned next to them.

I have failed to take the answer of one of the MC questions. Let me know if you found which one.
I would be very happy if you could correct the ones that are not right :smile:

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First one is weight

Reply 4114

MsFahima

20

Omg. I did not have enough time!! :'(
Guessed like some of the MC question. Fml.

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Reply 4115

Disney0702

9

Original post by Fred Cantoni

No. It's force.

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Yh thats what I thought as well. Did u put weight as your answer?

Reply 4116

Fred Cantoni

2

Original post by NEWT0N

This is an unfair advantage for you then, because if they decide to mark it as "150 ohms" then people who got confused by the "150 k ohms" will maybe have drawn a different current intercept due to the confusion. So they would have to mark it like this I think:

Any current less than the original current should get the first mark

Shallower gradient gets the second mark

Anyone agree?

Sounds fair!
What about the 3rd mark?

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Reply 4117

Absent Agent

21

Original post by QueNNch

Thanks for putting them!

I think you question 17 is incorrect because the question asked for the number on electrons on the NEGATIVE plate ONLY. Therefore the answer is half of what you got. (something like 2.2 x 10^30)

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Damn, yeah, if they asked for one of the plates only then its half

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Reply 4118

Alexie56

Original post by fruity97

Yeah what we're aqa playing at! Did they mean 150kohms? My graph was so small

Surely if they were charged with the same voltage the initial current should be the same. They were juat discharged through different resistors. So I drew a shallower graph?😕