Mass and Density

clwillingham

I would like to use sketchy physics to simulate a specific engineering problem that i am having in the real world. the problem has to doa a lot with a large number of 2.875 inch diameter wiffle balls. i was hoping to simulate this in sketchy physics, however i don't seem to be able to simulate the weight of them. i would like to simulate hollow balls not solid ones. so i would like to either change the density of the wiffle balls only, or else somehow hollow them out. i've tried so many methods but i can't seem to be able to do either things.

so how do i do this? is it possible to make a hollow ball in sketchup? or is it possible to change the mass or density of one object in sketchyphysics?

chaosss

If you got SP3x, you can change it in UI window.

SP3x download link.
http://code.google.com/p/sketchyphysics2/downloads/list?can=1&q=&sort=-uploaded&colspec=Filename%20Summary%20Uploaded%20Size%20DownloadCount

I attached an example.

d2.skp

clwillingham

well theres the problem . i had sketchy physics 3 RC1 instead of 3x. it works fine now. thanks for the help.

--edit--

another less important question: if i make a hollow sphere(i found out how to do it) is the mass really smaller or does it take into account only the outer sphere when i tell it to set the physics model to a sphere?

chaosss

Only the outer sphere matters.
Exactly speaking, SP takes the outher 'box-shaped boundary' of a group to calculate the mass of it.
So the shape dosen't matter.
If u click a group, you can see a box composed of blue lines. SP take total volume of the box and multiply it's density to calculate mass of the group.

clwillingham

i thaught that might be the case. but it doesn't matter that much. if i can adjust the density than i don't have to worry about much more. i was planning on using it only for concepts anyway. thanks again for all the help. this is about the best physics simulator i've used in a long time. it beats the Pro/Engineer mechanics simulator by a bit also .

juan974

hello, when you re done can you provide us a tutorial or explainations of your method (what is the goal of the exercice, what are your hypotheses, how do you exploit the results etc ...) please ...