Catapult and a Hollow Ball

  • #1
I'm building a catapult meant to fire a plastic ball as far as possible with the following items: 36 popsicle sticks, glue, 6 rubber bands, 4 clothes pins, a small stryofoam cup, and 4 feet of string. The ball has a radius of just under an inch, and it is very light. I am not meant to modify the ball in any way.

I have heard that to counter wind resistance you should aim it at a higher angle, maybe 50 rather than 45. Since it is so light, as in not dense, how much increase in angle should I compensate with?

Also I was wondering if anyone knew a proper, feasible way to make the ball travel a greater distance that won't comprimise the integrity of my catapult. I can upload a diagram of my catapult if necessary.
 

Answers and Replies

  • #2
PeterO
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I'm building a catapult meant to fire a plastic ball as far as possible with the following items: 36 popsicle sticks, glue, 6 rubber bands, 4 clothes pins, a small stryofoam cup, and 4 feet of string. The ball has a radius of just under an inch, and it is very light. I am not meant to modify the ball in any way.

I have heard that to counter wind resistance you should aim it at a higher angle, maybe 50 rather than 45. Since it is so light, as in not dense, how much increase in angle should I compensate with?

Also I was wondering if anyone knew a proper, feasible way to make the ball travel a greater distance that won't comprimise the integrity of my catapult. I can upload a diagram of my catapult if necessary.

That's what Research and Development is all about. I expect you would try different angles and see which one works best.
When you consider the flight of a table tennis ball which is spinning, you might try to impart some appropriate spin on your ball?
 
  • #3
That's what Research and Development is all about. I expect you would try different angles and see which one works best.
When you consider the flight of a table tennis ball which is spinning, you might try to impart some appropriate spin on your ball?
I had considered spin but I can't think of any solutions for that that aren't overly complicated. The problem is that it needs to spin forward, backwards is easy because it does it naturally, but forwards requires some trickyness.
 
  • #4
PeterO
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I had considered spin but I can't think of any solutions for that that aren't overly complicated. The problem is that it needs to spin forward, backwards is easy because it does it naturally, but forwards requires some trickyness.

Table tennis balls spinning backwards go further! Table tennis balls [and tennis balls] spinning forward dive down - landing short.
 
  • #5
Table tennis balls spinning backwards go further! Table tennis balls [and tennis balls] spinning forward dive down - landing short.

Ok, I see my errors in judgement now. After a little research I found out the lift comes from air pressure, not friction with the air. I think it's the Bernouli Affect that says when air is moving faster there is lower pressure. Since the air is freely flowing over the side spinning away from the direction thrown, it should be lifted that way. Thanks for correcting me, otherwise I would have never realized all this.
 

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