3
votes
1answer
42 views

Why does a piece of paper travels up when inserted into a kite's thread?

When I was young, I would insert a piece of paper into a kite's thread. The paper would travel upward till it reaches the head of that kite. What makes it to go up against the gravity even if the ...
1
vote
2answers
381 views

Toy helicopters at very high altitude

Because air is thin up there, toy helicopters usually have a maximum operational altitude. If the toy brought up by a real aircraft, higher than its intended maximum altitude, would it be able to ...
1
vote
3answers
156 views

How do birds generate thrust?

I have been watching this video carefully and I want to know how the wings of birds generate thrust. This is because the wings are more or less flapping up and down --- generating the lift. But I do ...
3
votes
1answer
66 views

Mathematically impossible for a vortex line to have loose ends?

Could someone show the math behind it? Source : "A vortex is a bunch of air circulating around itself. The axis around which the air is rotating is called a vortex line. It is mathematically ...
0
votes
0answers
61 views

Why does air circulate on an airfoil — The Kutta Condition

Why does the air circulate on a flowing airfoil, thus giving rise to increased velocity (circulation + relative airspeed) above the wing and hence decreased pressure.
0
votes
1answer
62 views

Airfoil theory — Why does air travel faster above? [duplicate]

I do not understand, why the air above the airfoil travels faster than the air below it? The air above has to travel faster than the air below so that both streams meet simultaneously at the ...
0
votes
4answers
278 views

How to end up with Newtons in the calculation of the lift force

In another StackExchange Physics question, @Rego had found the following equation to calculate the lift force generated by a simple rectangular blade. $$F = \omega^2 L^2 l\rho\sin^2\phi$$ in ...
2
votes
0answers
149 views

What is wrong with this downforce calculcation?

I tried calculating the downforce of a spoiler I need for a robot. I used this formula. $$F = \frac{1}{2}Ac_a\rho v^2$$ Where $\rho$ is air density, $v$ is the speed of my robot, $c_a$ is the lift ...
1
vote
0answers
107 views

effect of internal forces to a glider's descent

This is a continuation of a previous question, with more thinking applied, thanks to a helpful comment. Imagine a glider is airborne in a breezeless sky. The glider is 3 KM high, is traveling at 100 ...
12
votes
1answer
781 views

Do modern Formula One cars produce enough down-force to drive upside-down?

For example, if they were driving at top speed through a long tunnel, could they transition to and stay on the ceiling?
1
vote
1answer
1k views

Calculation for force generated by a rotating rectangular blade

When trying to calculate the lift force generated by a simple rectangular blade, I've found the following equation: $$F = \omega^2 L^2 l\rho\sin^2\phi$$ in which $\omega$ is the angular velocity, $L$ ...
-1
votes
1answer
487 views

Ping pong ball levitation control system question, modeling as a damper? [closed]

I am building a control system to levitate a ping pong ball at a given height in a clear plastic tube using an arduino and implementing PID control. I have to come up with a transfer function... I am ...
2
votes
1answer
3k views

Will a lighter car have a higher top speed than a heavier car with an equal power engine?

If I have a car (with a particular engine) optimized (shape & weight distribution-wise) for attaining the top speeds possible, and I put that engine into a car which is heavier (but otherwise the ...
4
votes
3answers
458 views

Why trimming the mainsail gives a larger torque to head up

I am learning sailing on a 5m catamaran (Nacra 5). I am familiar with basic aerodynamics and the physics of the sail and keel. We learned that when sailing closed hauled, too tight a mainsail tends ...
11
votes
4answers
1k views

Helicopter in an Elevator

You buy one of those remote control toy helicopters. You bring it into an elevator. The elevator goes up. Does the helicopter hit the floor or does the floor of the elevator push the air up into the ...
2
votes
3answers
200 views

Making a “heavier-than-air” craft float

How big would a hollow rigid object need to be to float, (not in water but in air) if all of the air was vacuumed out and the container sealed?
12
votes
4answers
1k views

How to sail downwind faster than the wind?

Recently a group set a record for sailing a wind-powered land vehicle directly down wind, and a speed faster than wind speed. Wikipedia has a page talking about it, but it doesn't explain exactly how ...