Tag Info

Accepted

How can a butterfly dodge the windshield of a fast moving car?

While @Nick gave a good answer (“air flows up and around the car”), that answer by itself would mean no bugs ever hit the windshield - and we know that is false. So what’s the difference between a bug ...
• 116k
Accepted

Why don't helicopters use reaction wheels to counter the main rotor?

You're talking about a device (in helicopters the tail fan imparting horizontal thrust) that counteracts the torque imparted on the main rotor (and therefore on the helicopter) by the surrounding air ...
• 85.1k

Why does a weather vane arrow point in the direction of the wind?

The vane has to be designed so that it has a preference to point in the right direction. In the example that you included, this is implemented by the flag at the back providing a broader cross section ...
• 4,761
Accepted

Why are aerodynamic / streamlined shapes always stumpy at the front?

You are correct if your boat will only travel in a straight line. In real life the motion of the boat will often have a yaw angle, so that it is moving slightly "sideways" relative to the ...
• 9,842
Accepted

Why do archery arrows tilt downwards in their descent?

The same reason objects which are heavier on one side tend to fall with the heavy side down: the tip of the arrow is denser than the rest of the arrow. The center of gravity is offset from its ...

Why do archery arrows tilt downwards in their descent?

Air. Conservation of angular momentum does infact dictate that whatever rotation it starts with it should end with, provided nothing else acts on it. Air allows its forward momentum to act on it. ...
• 2,225

Slipstreaming - is there a penalty?

The opposite seems to be true. There was, or maybe still is, a company that was looking into designing a system that allowed two semi trucks to "link" to each other (basically the truck in ...
• 1,170

Slipstreaming - is there a penalty?

For cycling, there doesn't seem to be a penalty, but even a small advantage to the rider in front of a group. Computational fluid dynamics simulations and wind tunnel testing have shown air resistance ...
• 461
Accepted

What does a wing do that an engine can't?

Let's look at the relationship between momentum and energy. As you know, for a mass $m$ kinetic energy is $\frac12mv^2$ and momentum is $mv$ - in other words energy is $\frac{p^2}{2m}$ Now to counter ...
• 116k