Just in time for Halloween, Ask Science looks at just what kind of science would be involved in a flying broomstick, and what forces would govern such a flight.
A few weeks ago, my family and I visited a castle where they filmed part of the first Harry Potter film. Despite the rich history of the castle, one of the biggest draws for visitors with young children is the daily broomstick flying lessons. My youngest daughter was quite excited about this, until about 5 minutes into the lesson when she realized the brooms didn’t actually fly. (A fact which I’m pretty sure we explained to her beforehand).
That experience made me wonder though, just what kind of science would be involved in a flying broomstick? What forces would govern such a flight? So just in time for Halloween, let’s take a look at the science of flying broomsticks.
Let’s start with the basics: getting that broomstick to hover off the ground with nobody on top of it.
Now if you remember from our discussion of Newton’s Laws, the First Law of Motion says that unless an outside force acts on our broomstick, it isn’t going to move anywhere. So in order for our broomstick to hover off of the ground, we need to apply an upward force, which we’ll call thrust. But how much thrust do we need?
The Gravity of the Situation
Well, as you probably know, the thing that keeps me, you, brooms, and witches from just flying off into the sky, is gravity.
Assuming we’re flying our brooms on Earth, the Earth’s gravity accelerates objects towards its center at 9.8 m/s².
Newton’s Second Law of Motion tells us the force that gravity applies to our broomstick is equal to the mass of the broomstick, multiplied by the gravitational acceleration. Amazon tells me that a traditional witch’s broom has a mass of about 1 kilogram. So we have:
Force of Gravity = 1 kg * 9.8 m/s² = 9.8 Newtons
This means the force of gravity acting on the broomstick is 9.8 Newtons.