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"There is nothing either good or bad, but thinking makes it so." ..."Shakespeare (154-1616, English dramatist and poet) "

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 Author Topic: Physics of collision showing forces at event for 1 dimension  (Read 4424 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
lookang
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http://weelookang.blogspot.com

 « Embed this message on: March 13, 2012, 02:01:30 pm » posted from:SINGAPORE,SINGAPORE,SINGAPORE

Dear Prof Hwang,

Ease of changing your own code:
reference:
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1435.msg8223#msg8223
This model is very similar to my own collision model,  i wish to study your implementation of contact forces inside your model.

My intent:

i am trying to change my own collision model http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=831.0 to include accurately the forces during impact.

Problem:

my implementation is flawed with this in-correct physics and i wish to get your help on this matter.
notice in the attachment pictures
t = 0 to t = t_collision = 0.295, momentum1 = m1*u1 = 8, Momentum2 = m2*u2, contact force = 0
t = t_collision+ dt = 0.30, momentum1 = m1*v1 = -4 , Momentum2 =not shown, contact force = maximum = -800
t = t_collision+ 2*dt to t_end of simulation, momentum1 = m1*v1 = -4 , Momentum2 = m2*v2 = not shown, contact force = 0
notice the physics (RED) is wrong, can you help make your model show contact forces correctly? I can study your model to learn

My Plan A:
my plan is to split the event handler into 2 parts,
t = 0 to t = t_collision, momentum1 = m1*u1 = , Momentum2 = m2*u2, contact force = 0
t = t_collision+ dt, momentum1 = (some midpoint to be calculated ) , Momentum2 = (some midpoint to be calculated), contact force = maximum
t = t_collision+ 2*dt to t_end of simulation, momentum1 = m1*v1, Momentum2 = m2*v2, contact force = 0
but i don't' know how to start the solution

Possible Plan B:
could be squeezing at peak force to show at t = t_collision+ dt/2
but i don't' know how to start the solution Is there a way to create a dt/2 inside the event?

My request:

can you demonstrate what you would do in your own model here http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=1435.msg8223#msg8223
You can implement the inclusion of contact forces whichever way you feel is correct physics, i will try to understand it!

 forces1.png (103.5 KB, 1277x990 - viewed 436 times.)  momentum1.png (105 KB, 1279x991 - viewed 421 times.) *** There are 1 more attached files. You need to login to acces it! « Last Edit: March 13, 2012, 02:18:23 pm by lookang » Logged
Fu-Kwun Hwang
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 « Embed this message Reply #1 on: March 13, 2012, 10:41:18 pm » posted from:Taipei,T'ai-pei,Taiwan

There is no way to find the force between two objects (when they collide with each other) without further information.
e.g. model for interaction between object when they collide.

You are welcomed to check out Simulate 1D collision with a virtual spring. A spring is used to model the collision process(spring constant depends on the softness of both objects).
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