A level maths

Hi,guys.I have a question here! While doing suvat problems of vertical motions,how exactly do I assign the sign conventions?For example,suppose a particle P is moving upwards from a fixed point O and a particle Q is moving downwards.Here,do I assign different sign conventions for P and Q?For example,for P,I take upwards as positive,and for Q,I take downwards as positive.Is it the case?

Reply 1

math4892

14

It does not matter whether you take 'up' or 'down' to be the positive direction, what matters is that you are consistent. So if you take up to be the positive direction, then any particle moving downwards has negative velocity. Similarly if you take down to be the positive direction, any particle moving up has negative velocity. I.e. two particles moving in opposite directions cannot both have positive velocity, since velocity is vector valued and is determined by both speed and direction.

(edited 7 months ago)

Reply 2

Anlasan

OP

12

Original post by Zebedi1

It does not matter whether you take 'up' or 'down' to be the positive direction, what matters is that you are consistent. So if you take up to be the positive direction, then any particle moving downwards has negative velocity. Similarly if you take down to be the positive direction, any particle moving up has negative velocity. I.e. two particles moving in opposite directions cannot both have positive velocity, since velocity is vector valued and is determined by both speed and direction.