!! LC Applied Maths 2016 Before and after

Appmaths97

Make sure you answer what being asked.
If it asks for velocity, dont leave it in i and j vector. make sure you give the magnitude and direction of the particle.
its an easy 5 marks to lose on a 30 mark question.

DownOneTourist

Appmaths97 wrote: »

Make sure you answer what being asked.
If it asks for velocity, dont leave it in i and j vector. make sure you give the magnitude and direction of the particle.
its an easy 5 marks to lose on a 30 mark question.

and the units!

adam240610

Do the easiest looking question first, could make a huge difference and stop the nerves early on.
If there's a huge mess of algebra left it's only worth 5 marks, move on and come back to it at the end, especially if you're pushed for time, nothing is more important than this tbh.

bookworm20

with oblique collisions if asked for the kinetic energy do you use the speed or just the "i" velocity

adam240610

bookworm20 wrote: »

with oblique collisions if asked for the kinetic energy do you use the speed or just the "i" velocity

1/2(m)(i^2+J^2)

You have to use both for kinetic, because if I is zero, it still has kinetic energy in the J

iFergal

bookworm20 wrote: »

with oblique collisions if asked for the kinetic energy do you use the speed or just the "i" velocity

Just use the i-component as the j-component will be the same and cancel out so unnecessary work. If we happen to get a collision along the j-axis (where the i will stay the same), the opposite - that did come up at least once.

Also, if you have multiple collisions, such as 3 spheres or a wall involved, kinetic energy after will use the final velocities after the collisions have taken place; intermediary velocities are irrelevant - just before and after.

Edit: In my experience it won't make a difference Adam. Hoping I'm correct now. :P

Misty_01

Can any body tell me why the initial velocity in the j sense for this question is 9.8 ?

A ball kicked from a point k on level ground hits the ground for the first time 30 m from k after a time of 2 s. The ball just passed over a wall standing 7.5 m from k.

Thanks

adam240610

iFergal wrote: »

Just use the i-component as the j-component will be the same and cancel out so unnecessary work. If we happen to get a collision along the j-axis (where the i will stay the same), the opposite - that did come up at least once.

Also, if you have multiple collisions, such as 3 spheres or a wall involved, kinetic energy after will use the final velocities after the collisions have taken place; intermediary velocities are irrelevant - just before and after.

Edit: In my experience it won't make a difference Adam. Hoping I'm correct now. :P

It makes it less complex, less likely to make a mistake if you include both :P

iFergal

It actually might be worth pointing out that if it's percentage loss, it'll be over the total kinetic energy (which will be i and j together), so that is an advantage of doing it your way!

I'll still probably stick to just i-components if it's just KE lost in joules though.

bookworm20

also if a question say the "actual" direction of a plane does this mean the direction it is trying go or does this mean the direction the wind is forcing it to go?

adam240610

May this exam not ruin the start to our (late) summers

Also can you rephrase that^ ?

iFergal

bookworm20 wrote: »

also if a question say the "actual" direction of a plane does this mean the direction it is trying go or does this mean the direction the wind is forcing it to go?

I think actual could really have two meanings here - and it should be obvious in the context of the question.

If it's in still air or the direction the plane must go, it is the direction it is trying to go in order to compensate for the wind. But in reality the wind is pulling it onto the course for it's destination, which could be interpreted as it's actual direction the plane is physically moving in. The phrasing and set up of the question should make it obvious what they are looking for.

bookworm20

That exam...was horrendous

DublinArnie

****ed up the exam, blanked out and forgot how to do the questions because of anxiety ffs.

Hoping to scrap a C3 with attempt marks and a few good questions (Q10, Q1).

adam240610

Question 1 and 2 were nasty, did 3-6 and 9-10 instead, was happy with the paper, hoping for an A2.

cgill

I quite liked that paper, I did 1,3,4,5,8,10 there were a few tough bits in part Bs but I thought it went well overall.

DownOneTourist

Q1 I didn't get a nice number for U but V was 15. The total distance was 101 point something for me
h didnt work for me.

Q3 happy with part a. I got point 61 for TB and 30 ish for the velocity of the ball at C
I got K equal to sin2theta+root3(1-cos2theta) so that was bad...

Q4 Happy with part a except I got the speed of P wrong.. I got the speed of q but forgot to half it because of the pulley system
part b again was weird for me. The 5g mass moved up for me as well as the 14g mass

Q5 I got the equations down in both questions. Part a was bad for me but part be was ok i think. I got either 18.4 or 71.6 degrees. I didnt say which it was but i wrote both of them into a diagram on the sheet.

Q9 Lovely part A. I got h equal to 4M over rowd squared i think
part b again was tough for me. I didn't know how resting on the the side of the take affected the rod so I got the moments around B let them equal to each other and got X over L equal to S-1

Q10 I got minus 18 for part a so I called that 18 meters. IDK
Part B was bangers

Bazinga_N

bookworm20 wrote: »

That exam...was horrendous

I completely agree, what a terrible way to end the exams!

iFergal

I did not really like that paper at all. Overall I feel likes it is really hard to know how you got on, especially when there was so few questions with show this is equal to this.

Q1 I got, it was fairly okay, not the easiest though.
Q2 Not nice. :P
Q3 This was fairly okay, it was definitely a weird setup and would have rathered a regular q3 but happy enough.
Q4 This has been worse, but has been easier.
Q5 Very weird... usually this question is very easy, but I'm happy with my answers.
Q6 For once I actually liked this, this can be very hit and miss but I think it went well overall.
Q8 Christ.
Q10 Part B (ii)... yeah...

DownOneTourist: I did too, it said distance though, and s is displacement so the minus is okay and you were correct to give your answer as +18. (Well, that's assuming we were right, but if we both got it...)

Appmaths97

iFergal wrote: »

I did not really like that paper at all. Overall I feel likes it is really hard to know how you got on, especially when there was so few questions with show this is equal to this.

Q1 I got, it was fairly okay, not the easiest though.
Q2 Not nice. :P
Q3 This was fairly okay, it was definitely a weird setup and would have rathered a regular q3 but happy enough.
Q4 This has been worse, but has been easier.
Q5 Very weird... usually this question is very easy, but I'm happy with my answers.
Q6 For once I actually liked this, this can be very hit and miss but I think it went well overall.
Q8 Christ.
Q10 Part B (ii)... yeah...

DownOneTourist: I did too, it said distance though, and s is displacement so the minus is okay and you were correct to give your answer as +18. (Well, that's assuming we were right, but if we both got it...)

i think it changed direction at t=2 so you had to get the displacement from 0 to 2 and the displacement from 2 to 3 to get the total disance.

DownOneTourist

Appmaths97 wrote: »

i think it changed direction at t=2 so you had to get the displacement from 0 to 2 and the displacement from 2 to 3 to get the total disance.

It does say" find the distance travelled by P between t=0 and t=3". So did I get the displacement rather than the distance?

Appmaths97

DownOneTourist wrote: »

It does say" find the distance travelled by P between t=0 and t=3". So did I get the displacement rather than the distance?

yeah i think so. did you get the time to change direction to be 2

iFergal

Appmaths97 wrote: »

i think it changed direction at t=2 so you had to get the displacement from 0 to 2 and the displacement from 2 to 3 to get the total disance.

Oh god my head really was not screwed on right this afternoon... I really got thrown by the paper overall... yeah that's right. Funny, I've done a very similar question multiple times in the past and I didn't even notice what I was doing wrong! :P

Oh and yeah, while you'd be getting displacement before and after t = 2, you'd still be taking absolute values as it's total distance travelled.

DownOneTourist

iFergal wrote: »

Oh god my head really was not screwed on right this afternoon... I really got thrown by the paper overall... yeah that's right. Funny, I've done a very similar question multiple times in the past and I didn't even notice what I was doing wrong! :P

Oh and yeah, while you'd be getting displacement before and after t = 2, you'd still be taking absolute values as it's total distance travelled.

I reckon it will be a common mistake if we both got thrown by it

onlinenerd

Q1- think I got the a part because of some basic geometry btw u=5
Atempted b but that was hard asf
Q2-the a part was nothing short of disaster
think I got the b part fully correct
Q3-Almost correct except maybe for working errors
Q4- Think I got maybe 40 on a good day
Q5 at first wtf but then might have gotten full marks
Q10- disaster especially the b part which dint even make sense

iFergal

DownOneTourist wrote: »

I reckon it will be a common mistake if we both got thrown by it

Yeah, I'd imagine so. It's a simple concept but so easy to overlook under exam pressure. I highly doubt I'm counting that question now anyway (honestly, not the one I expected to be excluding :rolleyes:).

Hopefully the marking schemes will be generous to us - last year's paper was a walk in the park compared to this realistically!

hubluh

Did we have to use calculus for Q3 b?

DownOneTourist

hubluh wrote: »

Did we have to use calculus for Q3 b?

You did for q2b. What makes you think you needed it for 3b?

iFergal

It was maximum range.

hubluh

DownOneTourist wrote: »

hubluh wrote: »

Did we have to use calculus for Q3 b?

You did for q2b. What makes you think you needed it for 3b?

It seems quite similar to 2013 Q3a where you had to use calculus.