# Help me in physic concepts to lift up the quadcopter.. using newton third law concepts..

Hello everyone.I have 1 question about quadcopter.. can you help me on how to prove the quadcopter can lift up by using physic law... if you have any physic calculation can share with me..

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A multicopter in hover can be explained by Newton's First Law.

When in a hover there are two equal and opposite forces at work keeping the net force at zero and therefore the change in velocity at zero.  One force (gravity) is pulling the copter downward.  This force at 1G is equal to the mass of the copter.  The opposing force is the cumulative thrust of the props.  When the thrust in a upward direction and force of gravity in a downward direction are equal there is no change in velocity.

Any excess thrust will cause the copter to begin to accelerate upward according to Newton's second Law. Conversely if the thrust is lower than the force of gravity it will begin to accelerate downward.

At a high level this explains how a copter can lift up. Neglecting drag you can calculate the rate of acceleration upward or downward for a copter of a given weight and for a given differnce in thrust  and gravitational forces on the copter..

If you want to calculate thrust from a rotating propeller from first principles this is a much more involved endeavor.

thx for information friends.

NASA states that lift is a force generated by turning a moving fluid - air in this case.   Here's the link to the NASA page explaining lift ...

http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html

http://www.grc.nasa.gov/WWW/K-12/airplane/right2.html

Specifically, here's the gist of it ... copied from the first link above ...

Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. Because air is a gas and the molecules are free to move about, any solid surface can deflect a flow. For an aircraft wing, both the upper and lower surfaces contribute to the flow turning. Neglecting the upper surface's part in turning the flow leads to an incorrect theory of lift.

An interesting experiment, is hovering a copter over a scale - the reading on the scale will closely match the weight of the copter - Newton's third law in action.

good information friends. I will study about it. thanks Tim Green. :)

thrust generated by propellers must be greater than weight of quadcopter

thx for information friends.

In order to take off, rise in altitude, accelerate forward and manuever this is true.  But for hover they must be equal.. Otherwise the coper is moving up or down.

If you are talking about the third law then I think of wind.

Gravity no.

Thrust no.

Wind yes.

When F2 = −F1

This means that F1 and F2 are equal in magnitude and opposite in direction.

Randy

thx for information friends.

Not sure if this is to may post but first and second law were referenced.

The third law does apply as well to hover where the force of air (first object) upward is equal to the force of the copter props downward against the air.  At a micro level this is effected by air molecules pushing against the prop surface.  Molecules on the bottom of the prop produce more force than ones on the top due to pressure and therefore density differneces.  More molecules pushing upwards than downwards.

i have assume for each motor will produce 15.9Newton. 15.9Newton will Multiply 4 motor = 63.6N
so 1newton= 100gram
63n= 6Kg.
I have calculate my total weight include battery casing camera frame and arm arounds 1.5Kg.
1.5Kg are suitable to fly my quadcopter..
but my lecturer want me to proof that quadcopter can fly by using physic teory...
Im stack at this situation...

Put a scale under the quad while it's hovering - have a big plate on the scale, to catch all of the air - the reading on the scale while the quad hovers inches above it, will just about match the weight of the quad.

And that demonstrates action and reaction.  The scale reading represents the momentum of the air, which was put their by the props on the quad.

So now the physics - the props on the quad react (action/reaction), to the action of having created that momentum of the air, with a force we call lift.

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## Contests

Season Two of the Trust Time Trial (T3) Contest has now begun. The fourth round is an accuracy round for multicopters, which requires contestants to fly a cube. The deadline is April 14th.

A list of all T3 contests is here

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