Hi please can I have help with this question:

A particle P is moving with constant velocity. The position vector of P at time t seconds (t 0) is r metres, relative to a fixed origin O, and is given by

r = (2t – 3)i + (4 – 5t)j

(a) Find the initial position vector of P.

The particle P passes through the point with position vector

(3.4i – 12j)m at time T seconds.

(b) Find the value of T.

(c) Find the speed of P.

I know how to work out part a but I’m stuck on part b as I’ve tried substituting known values into the

Rt=R0 + vt equation but I still can’t figure it out.

A particle P is moving with constant velocity. The position vector of P at time t seconds (t 0) is r metres, relative to a fixed origin O, and is given by

r = (2t – 3)i + (4 – 5t)j

(a) Find the initial position vector of P.

The particle P passes through the point with position vector

(3.4i – 12j)m at time T seconds.

(b) Find the value of T.

(c) Find the speed of P.

I know how to work out part a but I’m stuck on part b as I’ve tried substituting known values into the

Rt=R0 + vt equation but I still can’t figure it out.

Original post by mqb2766

Just pick either the i or j coordinate and solve for t so something like

4 - 5t = -12

4 - 5t = -12

Thanks! I realise my mistake now

Original post by mathcool

at t= 0 you know the position

at t= T you know the position by r.

so, calculate displacement (in i, j directions) at t=T by using the above

you can also calculate corresponding displacements using position at t=0 and by(3.4i – 12j)

the corresponding displacements must be what?

at t= T you know the position by r.

so, calculate displacement (in i, j directions) at t=T by using the above

you can also calculate corresponding displacements using position at t=0 and by(3.4i – 12j)

the corresponding displacements must be what?

Thanks!

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