I like to spend time outside when possible. On a recent adventure I took a couple of the kids to check out some trails near my mother's house. This particular place was pretty nice. It had a lake with some cliffs you could walk along. Note: Do not jump off the cliffs into the water—there is a $500 fine for that (at least that's what the sign said).
As we were standing near the edge of one of these cliffs, my daughter said that it wouldn't be too bad to jump off—it's not that high. I was pretty sure it was higher than she thought it is. But I don't have to just guess; we can measure the height with just a rock, my phone, and physics.
Here's what you do. Take your phone and get ready to record some video. Now drop the rock from rest so that it falls into the water. If you have to toss the rock, that's fine, as long as you only throw it horizontally. Don't throw it up or down—this will give an inaccurate measurement for the height. The only thing you need from the video is the time it takes the rock to fall and hit the water. From this time, we can calculate the height.
For my cliff, I got a free fall time of 1.3 seconds (I got this using Tracker Video Analysis—but there are lots of other programs to get the time).
Read more at Wired
Photo credit: Free-Photos via Pixabay
