You are Here: Home >< Maths

# mechanics 1 question ....help me plz ..its tomorrow!! watch

1. (Original post by bluefire)
what came from where ?? srry but i am really bad at such questions ...cant imagine them , also cant imagine whhat is going to happen tomorrow?!!!
come'on ....which part didnt you get??
2. (Original post by kosy91)
come'on ....which part didnt you get??
from where did 7i... and -15i and rest of them come from? plz clarofy further so that i could get it !
3. (Original post by bluefire)
what came from where ?? srry but i am really bad at such questions ...cant imagine them , also cant imagine whhat is going to happen tomorrow?!!!
Well, for it to be underneath point A, it has to have the same i component right? Imagine it in your head, point A and another point beneath it. If we are talking coordinates, both points will have the same X coordinate right? Therefore they will both have the same i component.

Now, you know that at time 7s, it is at ( 0, 0 ) with speed (2i - 3.5j) right?

So now you just need to know when it will reach below A. So imagine a point at A (7i - 10j), and ANOTHER point at the origin. The point at the origin moves right 2 and down 3.5 every second. Now you want the i components to be the same, so therefore it will take 7/2 s to reach below point A. Which is 3.5 seconds FROM Origin. Now you plus the 7 seconds before to giv you 10.5 seconds altogether

Now, you dont have to worry about it being north or south. Its going to be south, since the question states that it will.

GOod?
4. (Original post by bluefire)
from where did 7i... and -15i and rest of them come from? plz clarofy further so that i could get it !
well its just the same thing we did in part c). only difference is that we know u and the position vector it is at and just find t
5. (Original post by kosy91)
as for part d)

for it to be south of A, it must have the same i position.

therefore, 7i... + 3(-5i + ...) + t(ui + ...)= 7i

from above you know that u=2, so this gives you 7.5s

thus, total time is 3 + 7.5= 10.5s
from where did =7i come from in this ....7i... + 3(-5i + ...) + t(ui + ...)= 7i
6. (Original post by bluefire)
from where did =7i come from in this ....7i... + 3(-5i + ...) + t(ui + ...)= 7i
at time t seconds, it is south of A. A has position vector of 7i-10j. therefore for P to be south, it could be 7i-12j or 7i-100j....but the point is it has to be 7i
7. (Original post by kosy91)
at time t seconds, it is south of A. A has position vector of 7i-10j. therefore for P to be south, it could be 7i-12j or 7i-100j....but the point is it has to be 7i
i understood a little bit .....but its not a one night thing...i cant master it now...i might get strained and confused for other questions ...now i am going to get a good night sleep !!! in the afternoon its going to be m1 exam time ...do u think i could make it without this basic!!! thanks for all of your help guys!! appreciate it!!
8. ofcourse you can make it....dont worry....just do your best

BEST OF LUCK!!!!
9. (Original post by bluefire)
i understood a little bit .....but its not a one night thing...i cant master it now...i might get strained and confused for other questions ...now i am going to get a good night sleep !!! in the afternoon its going to be m1 exam time ...do u think i could make it without this basic!!! thanks for all of your help guys!! appreciate it!!
Didnt you understand my post? >__>
10. (Original post by kosy91)
ofcourse you can make it....dont worry....just do your best

BEST OF LUCK!!!!
really thnks alot for the encouragement!!! but i doubt it cuz other blunders might happen but i pray that everything goes perfect!! fingers crossed
11. (Original post by 2710)
Didnt you understand my post? >__>
i am sorry but am exhausted right now ...hope you don't mind it ...am sick also {FLU}..but still managed to cover majority of the portion just this thing vectors laft any how i will give it a best shot without it but still hope an easy one turns up!!
12. (Original post by 2710)
Didnt you understand my post? >__>
i liked your idea of visualising the vectors...most people fail to do that

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 14, 2010
Today on TSR

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams