Rigidbody2D bug?

[I use Unity 4.5.2f1]

0. Add two GOs to the new scene.
1. Add to both GOs RigidBody2D component and set Mass = 2, GravityScale = 0.
2. Add script to the first GO:

Code (CSharp):

1.   void FixedUpdate()
2.   {
3.       Rigidbody2D body = GetComponent<Rigidbody2D>();
4.       body.AddForce(new Vector2(0, -9.81f), ForceMode2D.Force);
5.   }

3. Add script to the second GO:

Code (CSharp):

1.   void FixedUpdate()
2.   {
3.       Rigidbody2D body = GetComponent<Rigidbody2D>();
4.       body.mass = 2;
5.       body.AddForce(new Vector2(0, -9.81f), ForceMode2D.Force);
6.   }

4. Run scene.

First GO will fall faster than second. Why??

 

Because it takes more force to get the body of mass 2 to start moving from a state of zero movement.

 

If they both start with a mass of 2 like you said, they fall at the same speed. If you don't see that, it's because the mass of the first one is different.

--Eric

 

I kind of disregarded that as a typo assuming the first one was left with the default mass of 1. So just to be sure that setting the mass = 2 each frame wasn't causing a bug, I tested it. They both move at the same speed if you set the mass to 2 in the inspector on both RB2D's. If you leave the first one with a mass of 1 like I assumed he did in the first place, then yes, the first falls faster because of the reason I posted above.

 

Mass of both objects equals 2. I set it using Inspector. In the script for second object I use the same mass.

I record short video with the problem: https://www.youtube.com/watch?list=...w&v=lqqfmHcMOEM&feature=player_detailpage#t=6

 

Strange. Update to 4.5.4 and try it. I did my tests in that version and didn't see that behavior.

 

After update all works as expected. It really was a bug in the old Unity version. Thanks for help!

 

Great!