## I noticed something strange

2 posts • Page

**1**of**1**### I noticed something strange

I did a little experiment, and i noticed something odd about the collective velocities of two objects bouncing in a room.

What I did:

I turned off gravity and air friction

I created four planes, which formed a small room.

I put a box and a circle in said room.

I made the planes, box, and circle have zero friction and 1 restitution.

I moved around the box and circle so they would be bouncing around, never losing energy.

The weird part:

I selected both of the objects and got a plot of them.

I selected velocity x over velocity y.

I noticed that the graph was only showing 90* or 180* turns, bending at right angles.

When i dragged the box, however, the graph showed squiggly meaningless readings.

When i let go of it, it started moving only at right angles again.

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Any mathematical reason why this would happen?

What I did:

I turned off gravity and air friction

I created four planes, which formed a small room.

I put a box and a circle in said room.

I made the planes, box, and circle have zero friction and 1 restitution.

I moved around the box and circle so they would be bouncing around, never losing energy.

The weird part:

I selected both of the objects and got a plot of them.

I selected velocity x over velocity y.

I noticed that the graph was only showing 90* or 180* turns, bending at right angles.

When i dragged the box, however, the graph showed squiggly meaningless readings.

When i let go of it, it started moving only at right angles again.

http://prntscr.com/cegjgp

Any mathematical reason why this would happen?

- unze2unze4
**Posts:**2**Joined:**Tue May 17, 2016 1:12 pm

### Re: I noticed something strange

The mathematical Reason behind this is that every time an object collides, it's velocity isbasically reflected once, and then stays until the next collision. In such a "reflection" the 2 velocity parts INSTANTLY jump from one value to the other, causing the 90° angles. When you drag an object, you keep changing the velocity all the time, which results in a squiggly curve. Unaltered, the velocity is always the same left for the collision changes.

- FRA32
**Posts:**213**Joined:**Wed Dec 03, 2014 9:51 pm

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