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

[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.

 

[Mark44]

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.

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

 

[1MileCrash]

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

 

[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.

 

[pwsnafu]

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

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.