Tagged Questions

1k views

How much more efficient is a road bike than a mountain bike? [closed]

What would be a good estimate on the difference of efficiency between a road bike and a mountain bike? A number of links cite all the usual reasons: thinner tires, better aerodynamics... But I'm ...
186 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 ...
74 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 ...
144 views

Spontaneous motion in a wind tunnel

Suppose that a hollow truncated cone is placed in a wind tunnel with a steady wind speed $V$. The cone is placed in such a way that it's base of area $A_1$ faces the wind (rather than the other side ...
1k views

Whats the anti-torque mechanism in horizontal take-off aircraft?

In most helicopters there is the anti-torque tail rotor to prevent the body from spinning in the opposite direction to the main rotor. What's the equivalent mechanism in horizontal takeoff single ...
858 views

What is the optimal weight for a golf ball?

I am 32 now, and have forgotten the basic physics formulas we used in school. I am sitting with a question that is bugging me. If I had to hit two golf balls of different weight with the same force, ...
143 views

Aircraft nose-up glide

In the pilot's introductory book "Stick and Rudder" it claims that a nose-up glide is possible. It doesn't state how, why or when. It implies it's possible to do and maintain a constant forward ...
397 views

Propeller modelling

I need a (very) approximate model of a propeller on an aircraft. My principal question is this: what would the relationship be between: Propeller rate of rotation Aircraft speed Force generated by ...
392 views

Bicycle Wheel Drag in Slipstream

I was recently driving behind a car that had a bicycle mounted on a carrier over the rear bumper. The bicycle wheels were not bound so they were rotating in the slip-stream of the car. I wonder, the ...
320 views

Why ballasted gliders fly faster

The fact: Gliders have ballast tanks that can be filled with water. The addition of ballast increases weight, and this allows the glider to fly at faster airspeeds while maintaining the same glide ...
1k views

Why airplanes fly: the final truth

The questions about the reasons the aircraft fly are frequent among scientist, since the high school until now, even if I work on the other side of fluid mysterious world (the Low Reynolds numbers ...