# Homework Help: Free Fall

1. Sep 25, 2007

### Robdog

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

Two ball are dropped from 5m high, Use 10 m/s^2 for the magnitude of the acceleration due to gravity.

2. Relevant equations

How do i start?

3. The attempt at a solution

not sure on how to start so i havent attempted:(

2. Sep 25, 2007

### Astronuc

Staff Emeritus
3. Sep 25, 2007

### Robdog

the problem asks how much time is elapsed during the fall of the 5.0m at a rate of 10m/s^2

Im sure there is an equation for this but i dont know which one or where to find it...

Last edited: Sep 25, 2007
4. Sep 25, 2007

### Astronuc

Staff Emeritus
If something starts at rest, i.e. with zero velocity, how far does is travel in time, t, if the acceleration is constant.

See - http://hyperphysics.phy-astr.gsu.edu/hbase/acons.html

The same concept applies for horizontal (x) or vertical (y) motion, provided the acceleration is constant.

5. Sep 25, 2007

### Robdog

so... y=1/2at^2... y equal to the hight of 5m? if so then i get 5m=1/2(10m/s^2)T^2 which = square root of 5.00s which = 2.24s??? but the that answer is still wrong. What did i do wrong.

6. Sep 25, 2007

### Robdog

o nvm should be the square root of 1.00s.... ill try that, wow i feel like an idiot... i need to sleep

7. Sep 25, 2007

### Astronuc

Staff Emeritus
Well - you figured it out. Do get some sleep, and refer to hyperphysics when the mind is more relaxed.