# Homework Help: How fast would it fall

1. Apr 9, 2015

### Flying Monkey

Hi All,

Can you help me, not a student (for a long time) but have a question that I need to answer.

I fly drones and I'm trying to work out the following:

If my 1.5kg drone fails at 400ft (122M) how long would it take to fall and hit the ground and what speed (max) would it be travelling on the way down.

Thank you so much,

Simon.

2. Apr 9, 2015

### Staff: Mentor

Hi Simon. It's hard to estimate, because we don't know what the wind resistance of such an object would be. It would be ideal if you had a second already-broken drone and could take it up and drop it as a test. Video its tumble and work out speed from the frames.

The shape and the unpowered rotors would slow down a drone's fall quite a lot, but Murphy's Law would still come into play---your drone crashing onto the only rock in sight for miles around.

There are sure to be videos of plummeting drones online, maybe there's one similar to yours? You may be able to estimate from that.

Good luck!

3. Apr 9, 2015

### Staff: Mentor

Do drones have basic fail mechanisms built in to remove power to all motors in the event of major failure? A mechanism to remove all power would at least stop it powering downwards and hitting at greater-than-freefall speed.