GCSE OCR 21st Century Triple Science (CBP1-7) Thread

Sadly I can't say with confidence no, but I can tell you that the people that I asked also got that. You could've calculated it by doing the first momentum (6x0.2) - the second momentum too (4x0.2) which is another way to do the change I believe.

That is the way I used but I then took away the second answer from the first one.

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Reply 1641

Swag>education

1

Are you ever wrong ARE YOU but a lot of people put what I did

Original post by Krollo

Surely the change in momentum was 2 kgm/s? As it is velocity you have to take into account the reversal of direction, don't you? I may be wrong.

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Reply 1642

Swag>education

1

Original post by Amyjonesx

I got 0.4 for the momentum one but i think its wrong :frown:

A lot of us got 0.4 but Krollo says its 2kg and he's right 99% of the time but sulfur said you could've worked it out to get 0.4

Reply 1643

Sulfur

OP

Original post by Swag>education

A lot of us got 0.4 but Krollo says its 2kg and he's right 99% of the time but sulfur said you could've worked it out to get 0.4

There were multiple ways of doing it apparently but I thought 0.4kg was sensible. A lot of people got that at my school. Saying that, it could be wrong though, I hope not!

Reply 1644

DDan123

8

What was the momentum question again?? Does anybody remember the values?

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Reply 1645

Sulfur

OP

Original post by DDan123

What was the momentum question again?? Does anybody remember the values?

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Something like a ball of mass 0.2kg travels at a speed of 6m/s. Then it hits the window and travels at a speed of 4m/s. Calculate the change in momentum.

Reply 1646

Krollo

17

Original post by Sulfur

Something like a ball of mass 0.2kg travels at a speed of 6m/s. Then it hits the window and travels at a speed of 4m/s. Calculate the change in momentum.

If I remember rightly, it said it bounced back (or words to that effect). In any case, it couldn't break the window. I hope.

Now, me in my overthinking logic reasoned like this. If it stopped when it hit the window, the change would be 0.8kgm/s. It doesn't make sense for it to be 0.4kgm/s if it changes direction, since it would be less than if it stopped. Since momentum is a measure of how hard things are to stop, clearly it takes more effort and so more of a change in momentum to change the direction, and get it speeding off again.

Since the formula for momentum concerns velocity, which has direction, the direct change in momentum must take the reversed direction as negative. Using this we get a change if 2kgm/s.

This does rely on the assumption that it rebounded, which made sense at the time since it only has 3.6 J of energy and so couldn't break through.

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Reply 1647

Sulfur

OP

Original post by Krollo

If I remember rightly, it said it bounced back (or words to that effect). In any case, it couldn't break the window. I hope.

Now, me in my overthinking logic reasoned like this. If it stopped when it hit the window, the change would be 0.8kgm/s. It doesn't make sense for it to be 0.4kgm/s if it changes direction, since it would be less than if it stopped. Since momentum is a measure of how hard things are to stop, clearly it takes more effort and so more of a change in momentum to change the direction, and get it speeding off again.

Since the formula for momentum concerns velocity, which has direction, the direct change in momentum must take the reversed direction as negative. Using this we get a change if 2kgm/s.

This does rely on the assumption that it rebounded, which made sense at the time since it only has 3.6 J of energy and so couldn't break through.

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It didn't break the window, yes and I'm pretty sure that it did rebound. Maybe you're right - I'll ask my teacher tomorrow if I get the chance. Since it was 1 mark there must've been a simple way of doing it so I'm unsure.

Reply 1648

Jillianmckeith

5

Were there questions about potential difference?

Reply 1649

username1344042

6

I've created a poll to find out which 1-6 exam people have found the most difficult. Please could everyone vote so we can predict the grade boundaries for each exam! Hopefully I can update it once the 7s have been sat.

The poll is in the same section as this thread, " Maths, science and technology academic help" Thanks :smile:

Reply 1650

HappyHylian

Ohhh crap I totally failed the six mark question on the bulb.. I said that the filiment is surrounded with mercury and when the electrons collide into the filiment it creates heat energy which makes the chemical potential energy in the mercury convert to light energy. ><

Reply 1651

LouiseDB42

Original post by Sulfur

It was the one underneath the E = mc2 question - it gave you a nuclear equation

I said that Gamma is stopped by lead and Beta is stopped by aluminium and lead, so Section A and Section B for beta and Section A for gamma too - because they can pass through the others, but if it can't pass through something and is blocked, you can detect the radiation from that. :confused:

I used that for the second part too with Alpha, since alpha can't penetrate paper/card.

That's exactly what I put! :smile:

I think that's what makes most sense

Reply 1652

Student.178

9

Original post by Sulfur

I thought it was 132 for top and 40 for bottom? I can't remember if they were my answers to be honest, but I think 40 was one of them and the other ended in a 2?

Yeah I also got 132 and 40, i think. Glad we both got it right! :smile:

Reply 1653

Sulfur

OP

Original post by LouiseDB42

That's exactly what I put! :smile:

I think that's what makes most sense

I thought that too - it also seemed right because you detect alpha (question underneath) since it couldn't pass through any of the materials.

Original post by JazzyT17

Yeah I also got 132 and 40, i think. Glad we both got it right! :smile:

When I did the maths, 132 and 40 all added and made sense... Phew! :smile:

Reply 1654

Student.178

9

Original post by Sulfur

I thought that too - it also seemed right because you detect alpha (question underneath) since it couldn't pass through any of the materials.

When I did the maths, 132 and 40 all added and made sense... Phew! :smile:

Yeah, I wasn't actually sure but when I added it up it all seemed to look ok so I sticked with it, I'm glad I did :smile:

how are you feeling about pbc-7 ? :biggrin:

(edited 9 years ago)

Reply 1655

Sulfur

OP

Original post by JazzyT17

Yeah, I wasn't actually sure but when I added it up it all seemed to look ok so I sticked with it, I'm glad I did :smile:

how are you feeling about pbc-7 ? :biggrin:

I need to do good on PBC 7 since they're the ones that'll tip the grade either forward or backward based off of PBC 1-6 - but I haven't even wrote my notes up for them yet nor looked at C7 at all, so I'm worried. I'm doing revision for them all over this final week. How are you feeling?

Reply 1656

physicalgraffiti

15

Went surprisingly better than I expected. But I only just realised how many more points I could've spoken about for the first 6 marker :tongue:

ah well... *crosses fingers for low grade boundaries* :biggrin:

At least we've almost finished the exams period though guys! Only three exams left for me now (the dreaded CBP7s...) How many exams does everyone else have left? :smile:

(edited 9 years ago)

Reply 1657

Swag>education

1

Original post by Sulfur

It didn't break the window, yes and I'm pretty sure that it did rebound. Maybe you're right - I'll ask my teacher tomorrow if I get the chance. Since it was 1 mark there must've been a simple way of doing it so I'm unsure.