- #1

Purity

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## Homework Statement

"A particle moves in the horizontal plane that contains the perpendicular unit vectors

**i**and

**j**. Initially it is at the origin and has velocity 18

**i**ms^-1. After accelerating for 10 seconds its velocity is (30

**i**+ 8

**j**)ms^-1. Assume that the acceleration of the particle is constant.

a) Find the acceleration of the particle

b) Find the position vector of the particle when the velocity is (36

**i**+ 12

**j**)ms^-1.

**2. The attempt at a solution**

For (a) i managed to find out the acceleration being (1.2

**i**+ 0.8

**j**)ms^-2 using v=at+u and rearranging it to a=(v-u)/t.

But for (b) it says the answer is 405

**i**+ 90

**j**

I've tried it over and over again but I don't think the question was specific enough (probably just me not understanding it).

I've tried it this way using:

u=18

**i**+ 0

**j**

v=36

**i**+ 12

**j**

t=10

R (position vector; i used R=(t/2)(u+v))=5(u+v) which gives the vector R= 240

**i**+ 40

**j**

I've tried it by replacing the initial velocity with 36

**i**+ 12

**j**but that didn't work either. I can probably work out the question if I understood what it basically is asking for.

Someone Please run me through this, I'm not good at mechanics :'(