Physics Fun
I forget, sometimes, how much I enjoy doing science...not just reading about it. Case in point:
http://www.technologyreview.com/view/510286/how-to-build-a-supersonic-ping-pong-gun/
That's right: a ping-pong ball gun that fires the ball at 1.2 mach. Very impressive.
So I got to thinking: could you do that demo in, say, a high school science classroom? What sort of backstop would you need? That's when I broke out the math.
KE = 1/2m * v^2
Mass is 2.5 grams, velocity is roughly 400 m/s
KE = 2000 Joules
That's a lot of joules, but it doesn't tell me much by itself as a "real world" number. So I did another equation (and yes, I coverted all of the listed measurements to a single metric standard before converting back to "real world" terms):
2000 Joules = 1/2m * 60mph ^2
M = 12 pounds.
Basically: if you were driving down the road and gentle tossed a frozen turkey out the window, it would hit with the same kinetic energy as a super-sonic ping-pong ball (give or take). Granted that the material properties of the ping-pong ball would likely case it to disintegrate rather than demolish, I _still_ don't think that'd be a very safe demo to perform in front of a classroom. Maybe on the football field or in the gym.
And yes: I actually figured this out for fun.
http://www.technologyreview.com/view/510286/how-to-build-a-supersonic-ping-pong-gun/
That's right: a ping-pong ball gun that fires the ball at 1.2 mach. Very impressive.
So I got to thinking: could you do that demo in, say, a high school science classroom? What sort of backstop would you need? That's when I broke out the math.
KE = 1/2m * v^2
Mass is 2.5 grams, velocity is roughly 400 m/s
KE = 2000 Joules
That's a lot of joules, but it doesn't tell me much by itself as a "real world" number. So I did another equation (and yes, I coverted all of the listed measurements to a single metric standard before converting back to "real world" terms):
2000 Joules = 1/2m * 60mph ^2
M = 12 pounds.
Basically: if you were driving down the road and gentle tossed a frozen turkey out the window, it would hit with the same kinetic energy as a super-sonic ping-pong ball (give or take). Granted that the material properties of the ping-pong ball would likely case it to disintegrate rather than demolish, I _still_ don't think that'd be a very safe demo to perform in front of a classroom. Maybe on the football field or in the gym.
And yes: I actually figured this out for fun.