How Fast Is Your Broomstick?
Everyday Einstein explains acceleration. Plus - how fast was Ron Weasley's Cleansweep flying?
Page 2 of 2
Naught to Seventy
As I mentioned earlier, I was never that into the car magazines that my friends were interested in, but I’ve always had an interest in fantasy novels, so let’s look at an example from Harry Potter. In Harry Potter and the Order of the Phoenix, Ron Weasley gets a new broomstick, a Cleansweep to be exact, which he brags can go “naught to seventy in ten seconds.”
Assuming Ron is measuring his velocity in miles per hour, naught to seventy, or 0 mph to 70 mph, is a measurement of acceleration. That is, if the broom starts out stationary (a velocity of 0 mph) and uses its maximum magical acceleration it’s capable of, 10 seconds later it will have a velocity of 70 mph.
As you’ve probably already figured out, the 0-60 measurement used in car magazines works the same way. Except that unfortunately, cars don’t fly.
What’s a Second Squared?
One of the things that often throws new physics students into a bit of confusion is that while velocity might be measured in meters per second, acceleration is typically measured in meters per second squared, or m/s2². Another way to think about this is that if something has an acceleration of 10 m/s2 what you’re really saying is that something accelerates 10 meters per second per second, or every second, the velocity goes up by 10 meters per second.
So if you start out at a standstill and start accelerating 10 meters per second per second north, after 1 second you’ll have velocity of 10 meters per second north, after 2 seconds your velocity will be 20 meters per second north, after three seconds, it will be 30 meters per second north, and so on, increasing by 10 meters per second ever second, or 10 meters per second squared.
So now you know what scientists think of when they hear the word acceleration, and you also know how to figure out which of your friends has the fastest broomstick (or car).