You are Here: Home >< Maths

# Mechanics Question - Resultant Forces watch

1. This question is driving me mad
I was revising for other exams and since I didn't have a mechanics exam everythings gone out the window

This question has totally stumped me, I drew a diagram but I don't even know if that's right. Anyway here's the full question:

Two forces, (4i - 5j)N and (pi + qj)N, act on a particle P of mass mkg. The resultant of the two forces is R. Given that R acts in a direction which is parallel to the vector (i - 2j),

(a) find the angle between R and the vector j

(b) show that 2p + q + 3 = 0

Given that also q = 1 and that P moves with an acceleration of magnitude 8(square root)5 m s^-2 ,

(c) find the value of m

Any help is appreciated
2. Bump

3. Bump
4. Oh well
5. a) find the angle between (i - 2j) and vector j. Vector R is parallel to (i -2j) which means it's simply a multiple of that vector.

b) dunno yet.

c) solve the equation to get p, then use the formula F=ma.

EDIT:

dokey, got b)

(4i - 5j) + (pi + qj) = (i - 2j)

4 + p = 1
q - 5 = -2

try to work from here
6. you have to times (i-2j) by k as it is parallel not equal...
so basically its like
4+p = k
-5+q = -2k
then u put them together and you'll get that answer
7. (Original post by tifflcy)
you have to times (i-2j) by k as it is parallel not equal...
so basically its like
4+p = k
-5+q = -2k
then u put them together and you'll get that answer
another five year old thread ...
8. (Original post by TeeEm)
another five year old thread ...
lol i was just looking for the answers when i was doin my hw then i figured it out
9. (Original post by tifflcy)
lol i was just looking for the answers when i was doin my hw then i figured it out
sure
10. Perhaps, like many equations where mass is equal to one, or slightly less than one, if you find some idea you can zero out, you are left with a binomial math problem, a choice between zero or one. My vote is that M, representing mass is less than or equal to one.
11. (Original post by Tellulater)
Perhaps, like many equations where mass is equal to one, or slightly less than one, if you find some idea you can zero out, you are left with a binomial math problem, a choice between zero or one. My vote is that M, representing mass is less than or equal to one.

### Related university courses

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: October 11, 2017
Today on TSR

### He lied about his age

Thought he was 19... really he's 14

### University open days

Wed, 25 Jul '18
2. University of Buckingham
Wed, 25 Jul '18
3. Bournemouth University
Wed, 1 Aug '18
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