6 ms·
Nice article, but I couldn't pass up a chance to correct Elon Musk's math: It is important to note that the amount of energy needed to achieve a given velocity
by panic 11y ago
Nice article, but I couldn't pass up a chance to correct Elon Musk's math:
It is important to note that the amount of energy needed to achieve a given velocity increases with the square, so going from 1000 km/h to 2000 km/h takes four times as much energy as going from 0 km/h to 1000 km/h, not twice as much.
Three times, not four--you already spent a quarter of the energy getting to 1000 km/h. Getting the rest of the way to 2000 km/h takes the remaining three quarters.
- notdonspaulding 11y agoI believe you've misunderstood his English. If it takes 1 Joule to accelerate the mass from 0-1000km/h, it will take 4 Joules to accelerate the same mass from 0-2000km/h. Elon is calling that four times as much as because he's considering the total energy required to accelerate from 0 in both numbers. I think you're just accounting for it differently by saying it takes 3 times as much as the original energy input to go from 1000km/h to 2000km/h. I'm a complete physics novice, I'm open to being schooled on this if I'm completely missing both yours and Elon's concepts here.
- pbreit 11y agoI don't think he worded it quite right but the inclusion of "not twice as much" makes it clearer that he was referring to "0 to 1,000" vs "0 to 2,000" (not 0 to 1,000 vs 1,000 to 2,000). So I believe the error was in the writing, not the math or understanding. Which he even pre-apologized for presumably in an attempt to assuage the nit-pickers.