# Free Fall Equations

1. Sep 25, 2007

### matace50

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

A hot-air ballon is descending at a rate of 2.0 m/s when a passenger drops a camera. If a camera is 45m above the ground when it is dropped, (a) how long does it take for the camera to reach the ground(b) what is the velocity just before it lands? Let upward be the positive direction for this problem.

2. Relevant equations
I have to use either 2a x change in displacement= final velocity^2 - initial velocity^2 or
change in displacement= 1/2a x t^2 + initial velocity x change in time

a = acceleration t= time ^2= squared x= multiply

3. The attempt at a solution

I think i somehow have to rearrange the equation to isolate t but i have no idea how. Can anyone help

2. Sep 25, 2007

### learningphysics

For the first part, use the equation:

d = v1*t + (1/2)at^2

careful about signs... decide first if you want upward to be positive, or downward to be positive...

3. Sep 25, 2007

### matace50

I see, but the problem doesnt give me time. I plugged everything in, but i still cant seem to get time.

(just started physics 2 weeks ago so im kind of confused)

4. Sep 25, 2007

### learningphysics

You have to use the quadratic formula to solve for time.

5. Sep 25, 2007

### matace50

Ok now i understand. Thanks