Why does the skin on a hot dog split longitudinally rather than circumferentially when you grill it?

Hoop stress on a cylindrical object is twice as large as longitudinal stress; therefore, a pressure vessel (hot dog) will rupture along the length before it will rupture radially.


At the end of their life, geostationary satellites are boosted up into a graveyard orbit. Why do they do this instead of having them re-enter Earth's atmosphere?

From a GEO orbit, it costs much less delta v to send a spacecraft into a graveyard orbit. For example, a GEO orbit traveling at about 4 km/s will need to spend close to 4 km/s to drop into a GTO and burn up whereas <.5 km/s can be spent on a transfer to a graveyard orbit.

renderGraveyard Orbit Example.png

Compare a belt drive vs. a chain drive vs. gears

Chains typically more efficiently transfer power, than belts, however, belt drives have many pros such as: less maintenance, less dirt, quieter. Gears transfer power more efficiently than belts and chains due to the lack of slip. Each of the three options have their place in mechanical systems, depending on power needed, precision required, and maintenance required. 


What materials would you use or avoid if you have an application with large temperature swings?

It would be best to avoid materials such as iron due to the amorphous structure. Fluctuating temperatures can cause steel to loose its properties from heat treatment. Nickel super alloy is a good choice because it can be made single crystal, only having one solid phase. Similarly, a binary system alloy would be a good choice. Kevlar, along with its high strength, is resistant to temperature changes and especially resilient to low temperatures.