Category Archives: Engineering

Q: Is it possible to parachute to Earth from orbit?

Physicist: Yes and no, but mostly no. It’s certainly possible to parachute safely to Earth from the top (or nearly the top) of the atmosphere, but this question isn’t about parachuting from space it’s about parachuting from orbit.  An orbit … Continue reading

Posted in -- By the Physicist, Engineering, Physics | 8 Comments

Q: How do I know my windmill is on straight?

The original question was: I got quite the challenge from my father in law. The problem is well defined, but I’m having difficulties finding a meaningful answer. The reason why he asked me is because I’m an engineering student and … Continue reading

Posted in -- By the Physicist, Engineering, Equations, Geometry, Math | 3 Comments

Q: Could the tidal forces of the Sun and Moon be used to generate power directly?

The original question was: If a machine enclosed in a building could, as I think it could, detect the tidal forces of the sun and moon upon the Earth could the effect be used to extract useful energy from those … Continue reading

Posted in -- By the Physicist, Astronomy, Engineering, Physics | 5 Comments

Q: Does opening a refrigerator cool down the room?

Physicist: Briefly yes, or no, not at all.  If you think of the room as including the inside of the refrigerator, then opening the door does nothing.  Otherwise, it does almost nothing.  But ultimately, if you leave the door open … Continue reading

Posted in -- By the Physicist, Engineering, Entropy/Information, Physics | 23 Comments

Q: How are voltage and current related to battery life? What is the difference between batteries with the same voltage, but different shapes or sizes? What about capacitors?

Physicist: Chemical batteries use a pair of chemical reactions to move charges from one terminal to the  other with a fixed voltage, usually 1.5 volts for most batteries you can buy in the store (although there are other kinds of … Continue reading

Posted in -- By the Physicist, Engineering, Physics | 26 Comments

Q: How many people riding bicycle generators would be needed, in an 8-hour working day, to equal or surpass the energy generated by an average nuclear power plant?

Physicist: A person on a bike can optimistically generate around 200 watts, and an average nuclear power plant generates 800 MW of power (although a big nuclear power plant generates many times more power than a small one). Given those … Continue reading

Posted in -- By the Physicist, Engineering | 1 Comment