Edexcel AS/A2 Mathematics M1 - 8th June 2016 - Official Thread

In momentum when two particles collide is the direction of motion of both of them always reversed?

Posted from TSR Mobile

No, it'll usually specify in the question.

Reply 781

thesuperdark

1

Original post by amelienine

doesn't matter i think, but i usually leave them as i and j as the final answer

ahh ok, it's just that I find it hard to work in the i + j form...I might just do all the working in the other form and then convert it in the end.

Thanks

Reply 782

KloppOClock

14

Original post by Clovers

In momentum when two particles collide is the direction of motion of both of them always reversed?

Posted from TSR Mobile

no they could join together, or one could change direction

Reply 783

JP0458B

16

When doing momentum/impulse questions, if you're told the two initial speeds and one speed after the collision, does it matter whether you put v or -v for the final speed you're trying to find?

Posted from TSR Mobile

Reply 784

KloppOClock

14

Original post by Don Joiner

When doing momentum/impulse questions, if you're told the two initial speeds and one speed after the collision, does it matter whether you put v or -v for the final speed you're trying to find?

Posted from TSR Mobile

turn your speeds into velocities, then solve for V. If V is positive you will get a positive result, etc

Reply 785

Don Pedro K.

9

Original post by KloppOClock

if you write both would you get the mark? do they only mark the correct work?

I'm not sure :s I wouldn't risk it tbh!

Reply 786

Zacken

22

Original post by Don Joiner

When doing momentum/impulse questions, if you're told the two initial speeds and one speed after the collision, does it matter whether you put v or -v for the final speed you're trying to find?

Posted from TSR Mobile

No, as long as you set one direction as positive then the sign of your answer will tell you what direction the particle moves after the collision. So stick with using only v, never -v.

Reply 787

Ppatel0

1

So do we need to know how to use unit vectors or not?

Reply 788

fpmaniac

2

How do you solve this question:
A particle p moves with constant acceleration (-3i+j). At time t seconds, its velocity is v. When t = 0, v = 5i-3j. Find the value of t when P is moving parallel to the vector i.

(edited 7 years ago)

Reply 789

KloppOClock

14

Original post by fpmaniac

How do you solve this question:
A particle p moves with constant acceleration (-3i+j). At time t seconds, its velocity is v. When t = 0, v = 5i-3j. Find the value of t when P is moving parallel to the vector.

parallel to which vector?

Reply 790

Not_a_horse

13

https://drive.google.com/file/d/0B1ZiqBksUHNYbDBBREF2ek9oUVk/view?pref=2&pli=1
Question 3, if I find W first then use it to calculate R, will I still get full marks, because the mark scheme says not.

Reply 791

Professor L

14

If I give my final answer correctly to 3 s.f. but the mark scheme only shows the answer as a fraction, will I get the answer mark? I'm really confused as they advise to give answers to 2/3 s.f. :s-smilie:

Reply 792

Don Pedro K.

9

Original post by Not_a_horse

https://drive.google.com/file/d/0B1ZiqBksUHNYbDBBREF2ek9oUVk/view?pref=2&pli=1
Question 3, if I find W first then use it to calculate R, will I still get full marks, because the mark scheme says not.

If the mark scheme says you won't, then I'm afraid that means you won't get the marks :s! I think it is because the first part specifically states "show that blah blah blah".

Reply 793

KloppOClock

14

Original post by Kamara7

If I give my final answer correctly to 3 s.f. but the mark scheme only shows the answer as a fraction, will I get the answer mark? I'm really confused as they advise to give answers to 2/3 s.f. :s-smilie:

if it says awrt then yes, if not, probably not.

Did you use an aproximation in your method such as g?

also if you wrote the answer as a fraction before you rounded it they should mark it correct and ignore subsequent working i think

Reply 794

Don Pedro K.

9

Original post by Kamara7

If I give my final answer correctly to 3 s.f. but the mark scheme only shows the answer as a fraction, will I get the answer mark? I'm really confused as they advise to give answers to 2/3 s.f. :s-smilie:

Question paper?

Reply 795

fpmaniac

2

Original post by KloppOClock

parallel to which vector?

oops. meant to say vector i.

Reply 796

KloppOClock

14

Original post by fpmaniac

oops. meant to say vector i.

when its parallel to i, the sum of the J components will be 0.

look at how you work out its current position r=r0+vt

then set the J component of the right hand side of that equation to 0, solve for t

Reply 797

JP0458B

16

Can anyone do this momentum/impulse question?

The mark scheme shows:

33/5mu = 2m(-v--4u)

I don't get how they've got both the 4u and the v as negative since the question States P is moving due east?

I can't make sense of it

Posted from TSR Mobile

Reply 798

fpmaniac

2

Original post by KloppOClock

when its parallel to i, the sum of the J components will be 0.

look at how you work out its current position r=r0+vt

then set the J component of the right hand side of that equation to 0, solve for t