# How to calculate the height of something by throwing an object off it?

1. Dec 1, 2011

### Bellabob

I go rock climbing a lot with my BSA troop, and my friends and I can only estimate the height. I want to know the exact height. Considering I do not have a ruler long enough to measure the height of the cliff, I know there is a way to throw an object off the cliff (say, a rock), time how long it takes to hit the ground, and then do some math and then you have the height.

I want to know how to do the math. Please be detailed with your answer, because I'm 15 and not really a math genius (I'm good, but not THAT good).

Thanks.

2. Dec 1, 2011

### Staff: Mentor

h = 16t2
t is in seconds and h is in feet.

3. Dec 1, 2011

### 1MileCrash

Make sure if you use mark's equation that the rock is either dropped or thrown straight ahead.

4. Dec 1, 2011

### DaveC426913

BTW, there are other ways that might have less error than estimating a time of a second or two.

You can figure out how far you are from the base of the cliff and use trig to calculate its height.

5. Dec 1, 2011

### pwsnafu

Damn you beat me.
But yes, trig is how it has always been down in the past. And we have GPS now, so it's easier too.