# Physics strange thing with polygon shape

Bugs will be moved here once resolved.

### » Sat Feb 06, 2016 11:33 pm

Problem Description
Two objects with same physics settings shared by family, but having two different polygon shapes will move in different way.

Attach a Capx
https://www.dropbox.com/s/mwc6x8ywshf72st/PhysicsGlitch.capx?dl=0

Description of Capx
Two physics objects with impulse applied to the right to see how they move. The red one is using "circle" for Physics collision mask property, the blue one is on "use collison polygon", wich is square. No gravity, no air friction or anything.

Steps to Reproduce Bug
• Create two same objects with physics.
• Set the firt one on circle collison mask, the second on collision polygon.
• Make them move the same way with no gravity.

Observed Result
The object with circle shape move faster than the one with collision polygon given the same impulse.

Expected Result
Objects with same mass given the same impulse should move at the same speed. Any thing i miss ?

Affected Browsers
• Chrome: (YES)
• NodeWK: (YES)
• Others: (NOT TESTED)

Operating System and Service Pack
Windows 7 SP 1

Construct 2 Version ID
Release 221 64 bit
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### » Sun Feb 07, 2016 12:24 am

Sprite has a mass of 16 whereas Sprite2 has a mass of 20.... I think you might be confusing density with mass.
Learning other engines, but C2 still rocks.
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### » Sun Feb 07, 2016 10:52 am

Ho, thanks. I really miss something. I saw the different mass in the debugger but how to set the mass in editor ? Both objects are same, I didn't set the mass.

Edit : Really sorry, I didn't search enough.
"Mass
The mass of the physics object, as calculated by the physics engine. This is the area of the object's collision mask multiplied by its density."
From the manual : https://www.scirra.com/manual/98/physics
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