M1 Vectors Question

I've attached the question I'm struggling with. I've understood everything, except part d.

I know why there's no i component, but I'm having trouble with why they're using the 9-2t=0 part.




Posted from TSR Mobile

If $(9-2t)\boldsymbol{i} + (-9+4t)\boldsymbol{j}$ has no $\boldsymbol{i}$ component then $(9-2t)$ must be equal to 0.

How come the answer from part b ie. the vector AB is used? I'm confused why you couldn't just use the actual position of A.

Thanks for your help!


Posted from TSR Mobile

Draw two points A and B where A is north of B on a set of axes. The position vector of A is the vector that goes from the origin to A. This vector could be any direction.

But the vector from A to B is the one that must be vertical i.e. have no $\boldsymbol{i}$ component.

And to work out the vector AB, you subtract the vector OA from the vector OB.

If you're still unsure, please let me know the exact part of this explanantion that doesn't make sense.

What is wrong with the labels these days?
New trend?
Why does this show as a Y9? A system bug?

What is wrong with the labels these days?
New trend?
Why does this show as a Y9? A system bug?

Well, can you help me with the above question ?

Posted from TSR Mobile

Yeah I've noticed that too. Seems like too many to be a coincidence.

Well, can you help me with the above question ?

Posted from TSR Mobile

Try substituting t=2 into the position vector and then draw it. Is that north-west?

Then think about how you can correct it.

OH!! Thank you , one last question when they give me a question like this, how can I immediately know if the / is negative before trying out and then figuring the right answer?

Posted from TSR Mobile

Nvm I knew it and thank you!!

Posted from TSR Mobile

Thanking youself is the first sign of madness.