# Homework Help: Mechanics Projectile Questions

1. Jan 15, 2008

### thomas49th

1. The problem statement, all variables and given/known data
At time t = 0 a particle is projected horizontally from a point A with position vector (5i + 30j)m. It passes through point B with position vector (17i +10.4j)m. Find:
- Its speed of projection
- Time taken to travel from A to B

2. Relevant equations

s = ut + 0.5at²

v² = u² + 2as

v = s / t

a = (v - u) / t

v = s / t
3. The attempt at a solution

Well from A to B the i and j components are

12i
-19.6j

i can draw a right angled triangle and use pythagerous's thyrom and calculate that the other side is 12.8 (3.s.f) - is that meters?

Have i gone the right way. I don't know what to do now. Any hints

2. Jan 15, 2008

### thomas49th

Ahh i worked out the verticle component and got t = 2

now...

3. Jan 15, 2008

### thomas49th

then put this into v = s / t

v = 6m/s and t = 2s

yeh :)

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