# I need help in verticle motion

1. May 5, 2005

### heaven eye

child play with cubes , he threw first one vertically to up with velocity of (v), after five seconds he threw second cube vertically to up with the same velocity , two cubes collided at 9 meter height what the velocity of two cube? (they are the same!)

and thank you all again , again , and again :tongue: .

2. May 5, 2005

### The Bob

You want to use $$s = ut + \frac{1}{2}at^2$$ and $$v^2 = u^2 + 2as$$ setting s to 9 each time. Then the two equal each other and you can find a time as you know the acceleration and the time in each case.

Last edited: May 5, 2005
3. May 5, 2005

### dextercioby

You should write the equation of motion in vector form

$$\vec{r}(t)=\vec{r}_{0}+\vec{v}_{0}t+\frac{1}{2}\vec{a}t^{2}$$

and then choose an axis along which the movement takes place,an origin for this axis, then a sense on this axis and then do the projection of the vector equality on this axis...

This is just the beginning,but it's essential.

Daniel.