How fast does a multi-copter drone need to fly in order to freefall on the other side of a highway if:

Drone weight - 15kg, 20kg
Highway width - 70 ft
altitude above ground - 200 ft, 300 ft, not determined
See iamge


  • 5
    $\begingroup$ This looks like homework with no attempt at a solution. $\endgroup$ – Transistor Jun 27 '19 at 16:58
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    $\begingroup$ And if it's unpowered, neglecting friction, then it's not really an aviation question as it doesn't matter if it's a drone or a cannonball, it's a basic projectile physics question. $\endgroup$ – fooot Jun 27 '19 at 17:35
  • $\begingroup$ @Transistor homework or research for a smuggling project :') $\endgroup$ – Quentin H Jun 28 '19 at 8:08

The time for a free falling object to hit the ground can be calculated with the formula

s = 1/2 * a * t^2

solved for t this is


with a being the acceleration (in this case a = g = 9.81 m/s) and s elevation in meters above ground.

Once you have calculated this time, you can calculate the distance the object travels horizontally during that falling process by simply multiplying horizontal speed of the object in meters per second by the time in seconds.

Notes: These formulas are based on the assumptions that there is no friction (meaning vacuum in this case). This is obviously not perfectly correct and especially airfoil objects will have a massively different behavior depending on the surrounding air, but this is the basic physics.

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    $\begingroup$ I am intentionally not providing the final formula here, as it looks like this is some kind of homework and you should solve it on your own. Therefore I mentioned the basics but leave the work of combining and solving formulas to you. $\endgroup$ – rauberdaniel Jun 27 '19 at 17:41

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