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April 14th, 2015, 04:36 AM  #1 
Newbie Joined: Apr 2015 From: UK Posts: 3 Thanks: 0  How deep will a circle sit into a right angle
Hi, I'm building a toy for my kids whereby a table tennis ball is going to run along troughs made from rightangled pvc corner pieces. The troughs will be held in place by magnetic struts. I need to cut through the corner pieces to have slots into which the struts can be places on which the pvc will sit. The table tennis balls are 40mm in diameter the pvc sides are 25mm in length either side. How far in can/should my slots be in order to give maximum support, without risking the balls getting stuck on the struts? I know the hypotenuse is sqrt(2*25mm^2) ~ 35mm. I know the equation for the arc of a circle sqrt(r^2  x^2), but I can't figure how to combine the two to get the deepest point that the circle/sphere will reach, or indeed, if this is the correct approach. Any ideas? Last edited by skipjack; April 14th, 2015 at 08:36 AM. 
April 14th, 2015, 06:05 AM  #2 
Newbie Joined: Apr 2015 From: UK Posts: 3 Thanks: 0 
OK, think I figured it. Of course it's noting to do with the size of the pvc (as it's greater than the radius of the sphere), so it's just the hypotenuse of a 20mm X 20m rightangled triangle minus the radius of the 20mm circle ~ sqrt((400 + 400))  20 ~ 8.28mm
Last edited by skipjack; April 14th, 2015 at 08:34 AM. 
April 14th, 2015, 08:37 AM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,379 Thanks: 2011 
That seems correct. What will the magnetic struts be magnetically adhering to?

April 19th, 2015, 12:55 PM  #4 
Newbie Joined: Apr 2015 From: UK Posts: 3 Thanks: 0 
I'm going to attach the magnets to a large magnetic whiteboard, at first at least. I'm hoping to make something like this, if the first iteration is successful: https://www.facebook.com/rob.bane/vi...2863841555656/ i.e. with a larger surface, but struggling to find a costandweight effective large magnetic surface: Last edited by robbane28; April 19th, 2015 at 01:00 PM. Reason: typo 

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angle, circle, deep, sit 
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