Calculating the speed air comes out of a fan

[bigbob512]

TL;DR Summary

If i have a drone with four propellers with a mass of m = 0.42kg, the diameter of each blade d = 0.21m and the air density is 1.3 kg/m3. How do i calculate the speed which air comes out with. Your help will be much appreciated, thank you.

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Hi, I have a task where i have to calculate the speed of which the air is flowing out of a drones propeller fan.
This is all i have been given:
The mass of the drone m = 0.42kg, There are four propellers the lenght of each blade d = 0.21m, the air density is 1.3 kg/m3 and g=10 m/s^2y. And the propellers generate enough force to keep the drone in a rest position in the sky. How do i calculate the speed which air comes out with. Your help will be much appreciated, thank you.

 

[jrmichler]

Here's how I would attack this problem:

1) Assume that the weight of the drone is equally distributed between the propellers.

2) Search using terms propeller thrust equation. One of the first hits is this one: https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/thrust-equation/. It's hovering, so assume that the free stream velocity is 0, and solve.