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# M2 wjec 2016- Official thread watch

1. (Original post by SoThisIsStresful)
what did people get for k in the first question? i got 1.5 but most people i spoke to had different :/
I got 1.5 but only because I couldn't work out how to do it so figured I'd just play around with it and get any value I could so that I could at least do the second part of the question and get ecf on that even if I was wrong for part a).
2. (Original post by siri29)
how did people do the cannon question?
Momentum, a bit mean tbh because it's not on the spec this year. for b.) the start energy is equal to the kinetic energy of the cannon and the ball added using 1/2mv^2 for both. and c.) uses the KE of the cannon and the distance travelled using work=force*distance.
hope that helps clear it up
3. (Original post by SoThisIsStresful)
Momentum, a bit mean tbh because it's not on the spec this year. for b.) the start energy is equal to the kinetic energy of the cannon and the ball added using 1/2mv^2 for both. and c.) uses the KE of the cannon and the distance travelled using work=force*distance.
hope that helps clear it up
And for the assumption, did you put down that all the energy from burning the charge is converted to KE for the recoiling part and the cannon ball, and none is converted to sound, heat, etc.?

Also, at least it's from a previous mechanics module - last year they had double angle formulae in the M2 paper.
4. (Original post by SoThisIsStresful)
c.) uses the KE of the cannon and the distance travelled using work=force*distance.
hope that helps clear it up
I did this differently... What did you get for the magnitude of the force needed to stop the recoiling part in a distance of 1.2 m?
5. (Original post by Hydeman)
And for the assumption, did you put down that all the energy from burning the charge is converted to KE for the recoiling part and the cannon ball, and none is converted to sound, heat, etc.?

Also, at least it's from a previous mechanics module - last year they had double angle formulae in the M2 paper.
I said it was an isolated system (no other forces acting, no loss through sound, air resistance, heat etc.). yeah Im just glad i had PH4 yesterday for that one!
6. (Original post by Hydeman)
I did this differently... What did you get for the magnitude of the force needed to stop the recoiling part in a distance of 1.2 m?
total KE of ONLY cannon recoiling = 0.5*1600*4.5^2 =16200J <----- this is also work needed to stop it from moving.
work=force*distance
force=16200/1.2=13500N me thinks

i have the paper here so it was easier just to re do it, hope that helps
7. (Original post by SoThisIsStresful)
total KE of ONLY cannon recoiling = 0.5*1600*4.5^2 =16200J <----- this is also work needed to stop it from moving.
work=force*distance
force=16200/1.2=13500N me thinks
I got double that using a different method. Hope C3/C4 boundaries are the same as last year; then it won't matter what result I get in M2.

i have the paper here so it was easier just to re do it, hope that helps
Can you post a picture of it?
8. I too had 1.5 for k. I remember getting 21/14 and then simplifying it to 3/2.
9. Attachment 554199554201
Attached Images

10. (Original post by Hydeman)
I got double that using a different method. Hope C3/C4 boundaries are the same as last year; then it won't matter what result I get in M2.

Can you post a picture of it?
just done hope it worked, sorry it's bad quality :/
11. (Original post by SoThisIsStresful)
just done hope it worked, sorry it's bad quality :/
Thanks.

What do you think the grade boundaries will be like? I feel like it should be similar to 2013 (considering the unusual circles question about the disc and that people who don't take physics and forgot all of M1 are likely to be thrown by the momentum question), but then I felt the same about last year's paper, and it ended up being 62/75 for an A.
12. (Original post by Hydeman)
Thanks.

What do you think the grade boundaries will be like? I feel like it should be similar to 2013 (considering the unusual circles question about the disc and that people who don't take physics and forgot all of M1 are likely to be thrown by the momentum question), but then I felt the same about last year's paper, and it ended up being 62/75 for an A.
Honestly I have no idea, i tend not to look at grade boundaries until results day :/ i think your right though, some people i spoke to (that don't do physics) didn't even try the momentum and circles question because they had no idea. Good luck all the same
13. (Original post by Hydeman)
Momentum before = momentum after for part a).
Can't remember part b) but I did do it.
Part c) was F = (m(v - u))/t, I think. You had to use time = distance/speed first though.
I thought it was Just work = force x distance
14. (Original post by matthewdjones)
I thought it was Just work = force x distance
I might have done that wrong. Another person (see above) did it using work = Fs and got an answer that was half of what I got.
15. (Original post by SoThisIsStresful)
Honestly I have no idea, i tend not to look at grade boundaries until results day :/ i think your right though, some people i spoke to (that don't do physics) didn't even try the momentum and circles question because they had no idea. Good luck all the same
Good luck to you too.
I did put some stuff down for the weird circles question, and mentioned that the units of angular velocity are radians per second, just in case there's a mark for that.

Just hoping C3 and C4 boundaries are generous; if they are, it won't matter what I get in M2.
16. (Original post by SoThisIsStresful)
Momentum, a bit mean tbh because it's not on the spec this year. for b.) the start energy is equal to the kinetic energy of the cannon and the ball added using 1/2mv^2 for both. and c.) uses the KE of the cannon and the distance travelled using work=force*distance.
hope that helps clear it up
i was going to do momentum but i did kinetic energy calc instead oops, but i used the same method for the rest. oh well hopefully didn't lose too many
17. (Original post by matthewdjones)
I thought it was Just work = force x distance
i actually used suvat equations and then used f=ma
18. (Original post by siri29)
i actually used suvat equations and then used f=ma
Could you assume constant acceleration?
19. (Original post by matthewdjones)
Could you assume constant acceleration?
i took s=1.2 u= 0 (as it is at rest at the start) v=whatever you got and then calculate a and sub into f=ma
20. (Original post by SoThisIsStresful)
yeah, not bad tbh. I wasn't keen on the big blocks of questions with no parts and the momentum was a nice surprise (would not have managed that if i didn't do physics though) what did people get for k in the first question? i got 1.5 but most people i spoke to had different :/
I got that

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