# At what height objects will pass each other?

1. Jan 25, 2014

### patelneel1994

1. The problem statement, all variables and given/known data

An object is thrown downward with an initial (t = 0) speed of 10 m/s from a height of 60 m above the ground. At the same instant (t = 0), a second object is propelled vertically upward from ground level with a speed of 40 m/s. At what height above the ground will the two objects pass each other?

first object
t0 = 0
V = 10 m/s
H = 60
Second object
t0 = 0
V = 40 m/s
H = 60
2. Relevant equations
d = Vi . t + 1/2 a t2

3. The attempt at a solution
This equation doesn't see me to work since we need to find at which height objects will pass

2. Jan 25, 2014

### tiny-tim

hi patelneel1994!

call the height of either object above the ground "d", and rememb
er that the two objects start at different values of d …

show us what you get

3. Jan 25, 2014

### patelneel1994

So instead of d I should put h. Find height for each object separately!

4. Jan 25, 2014

### tiny-tim

d or h, it doesn't matter, so long as you use the same symbol for each, but start them at different values

5. Jan 25, 2014

### patelneel1994

I got 41 m. Thanks

6. Jan 25, 2014

### haruspex

I confirm that answer. A slightly quicker way, perhaps, is to note that the two objects undergo the same acceleration, so the relative velocity is constant. The closing speed is therefore a constant 10+40=50 m/s. That tells you how long they take to meet.