[koat]

hello


Could somebody expalin to me how to work out question 3i of this paper
see link to paper below

http://www.mei.org.uk/files/papers/2011_June_m1.pdf

what are the general rules when working out questions like that?

thanks a lot in advance

[Andythepiano]

I would just translate the info into something more meaningful to yourself - eg equations in the x- and y- directions and solve.

[acomber]

(Original post by Andythepiano)
I would just translate the info into something more meaningful to yourself - eg equations in the x- and y- directions and solve.

I am puzzled by this too. you only have one x coordinate in F, not the equation of the line, so G could be parallel in many ways. So how can you work this out???

[getenoughsuarez]

Lines which are parallel have a common multiple. In this case, we can see from the x in line F is is -2 and in G is -6. Therefore we can assume that the multiple is 3. And therefore if we multiply y and z by 3. y=3 x 3 and z = -4x 3

Hope i helped.

[koat]

(Original post by getenoughsuarez)
Lines which are parallel have a common multiple. In this case, we can see from the x in line F is is -2 and in G is -6. Therefore we can assume that the multiple is 3. And therefore if we multiply y and z by 3. y=3 x 3 and z = -4x 3

Hope i helped.

thanks a lot

could you also help me with that:
the mei jun09 paper question 2iii
im really stuck ....

thanks

http://www.mei.org.uk/files/papers/m109ju_livn.pdf

[getenoughsuarez]

I'll be honest with you i got it wrong. But i get why the answer is the answer.

scalar only has magnitude and no direction therefore the its going to be the same as t1 but on fig.2 it is in the negative i direction. (I got 10 then i thought it was wrong because its was in the positive direction). Turns out i was right and it was -10.
t1+t2=w since its in equilibrium and therefore (10i+24j)+(-10i+10j) = 34j and w(lowercase) is magnitude so we square and then square root 34 which = 34

i've got this exam on friday aswell not looking to forward to it..answering your questions is helping my confidence lol

[koat]

(Original post by getenoughsuarez)
I'll be honest with you i got it wrong. But i get why the answer is the answer.

scalar only has magnitude and no direction therefore the its going to be the same as t1 but on fig.2 it is in the negative i direction. (I got 10 then i thought it was wrong because its was in the positive direction). Turns out i was right and it was -10.
t1+t2=w since its in equilibrium and therefore (10i+24j)+(-10i+10j) = 34j and w(lowercase) is magnitude so we square and then square root 34 which = 34

i've got this exam on friday aswell not looking to forward to it..answering your questions is helping my confidence lol

thanks
do you also know how to do that and i dont really get 4ii) in jun06
"deduce that...."


http://www.mei.org.uk/files/papers/m106ju_hwi4.pdf

[koat]

(Original post by getenoughsuarez)
I'll be honest with you i got it wrong. But i get why the answer is the answer.

scalar only has magnitude and no direction therefore the its going to be the same as t1 but on fig.2 it is in the negative i direction. (I got 10 then i thought it was wrong because its was in the positive direction). Turns out i was right and it was -10.
t1+t2=w since its in equilibrium and therefore (10i+24j)+(-10i+10j) = 34j and w(lowercase) is magnitude so we square and then square root 34 which = 34

i've got this exam on friday aswell not looking to forward to it..answering your questions is helping my confidence lol

to be honest with you i dont quite understand why i components of T1 and T2 are the same? how do you know that?

[getenoughsuarez]

(Original post by koat)
to be honest with you i dont quite understand why i components of T1 and T2 are the same? how do you know that?

the i components are the same because it says that k is a scalar, and therefore it is the same.

as for question 4 part ii - they give us the position vector of r =3ti + (18t^2-1)
This is the same as the displacement. we know that differential of the displacement(ds/dt) = the velocity. Therefore the v = 3i+36tj

For your part of the question. Deduce just means show/explain and since it wants to to say why it can never go in the j direction. You simply say for the particle to go in the j direction, i must = 0. However as you just showed velocity is 3i+36tj. So i is always a constant of 3 and therefore the particle can never travel in the j direction.

[koat]

(Original post by getenoughsuarez)
the i components are the same because it says that k is a scalar, and therefore it is the same.

i thought scalar means it has a magnitude only???

[getenoughsuarez]

(Original post by koat)
i thought scalar means it has a magnitude only???

that's right. Sorry ignore what i previously said. We can see that W is straight down(since weight is always straight down) and therefore it has no i component.
Therefore the 2 i's in the tensions HAVE to cancel out. It is for this reason we know that it has to be -10 since (10i+24j) + (ki+10j) has to equal 0 for i.

Sorry about before my reasoning was wrong. But i am quite sure this explanation is correct.

[koat]

(Original post by getenoughsuarez)

For your part of the question. Deduce just means show/explain and since it wants to to say why it can never go in the j direction. You simply say for the particle to go in the j direction, i must = 0.

ok i understand but i was just wondering why i has to be zero?

[koat]

(Original post by getenoughsuarez)
that's right. Sorry ignore what i previously said. We can see that W is straight down(since weight is always straight down) and therefore it has no i component.
Therefore the 2 i's in the tensions HAVE to cancel out. It is for this reason we know that it has to be -10 since (10i+24j) + (ki+10j) has to equal 0 for i.

Sorry about before my reasoning was wrong. But i am quite sure this explanation is correct.

ahhh i understand
thanks

[getenoughsuarez]

(Original post by koat)
ok i understand but i was just wondering why i has to be zero?

draw a graph take i for x and j for y.
To go directly in the y direction(j) as this questions asks x(i) has to equal 0.

for the particle to go in a direction - solely in that direction the other components have to = 0.

i hope this made sense, sounds abit waffly but i hope the point comes across.

[koat]

(Original post by getenoughsuarez)
draw a graph take i for x and j for y.
To go directly in the y direction(j) as this questions asks x(i) has to equal 0.

for the particle to go in a direction - solely in that direction the other components have to = 0.

i hope this made sense, sounds abit waffly but i hope the point comes across.

thanks a lot
can i ask you a last thing
its this:


jun08 2i) how do you draw the sketch
its not shown in the mark scheme

thanks again


http://www.mei.org.uk/files/papers/m108ju_vik3.pdf

[getenoughsuarez]

(Original post by koat)
thanks a lot
can i ask you a last thing
its this:


jun08 2i) how do you draw the sketch
its not shown in the mark scheme

thanks again


http://www.mei.org.uk/files/papers/m108ju_vik3.pdf

A line going from the origin (0,0) to (4,-5) with an arrow.

[koat]

(Original post by getenoughsuarez)
A line going from the origin (0,0) to (4,-5) with an arrow.

thanks a lot

do you know how to do qu. 7v from that
http://www.mei.org.uk/files/papers/m110ja_4761.pdf