1. Mar 20, 2006

### Jess1986

This is a follow from a post i made yesterday. The question is:

2 particles are projected vertically up one after another from the same point at same initial speed u. T is the time interval between the 2 projections, where T<2u/g. Find what further time elapses before the particles collide, and find their speeds immediately before impact.

The equations i have found so far are for distance travelled
x= -0.5gt^2 + ut.
However i have realised this formula is for the distance the particle has travelled rather then the height reached. Since i need to find the time when the particles will collide (ie when they are at the same height) i am stuck as i think the formula is no use?! Please help

2. Mar 20, 2006

### arunbg

Hint : x is not actual distance but displacement.
Can u go from here?

3. Mar 20, 2006

### Jess1986

so i should equate the equations for x for both particles? how would i substitute T into the equation for particle 2?

4. Mar 20, 2006

### arunbg

Yes u should equate x.

Take t as time for first proj. and t-T for second proj.
Solve for t in terms of T.

5. Mar 20, 2006

### Jess1986

ok thats great thanks for your helpx