I've been working some with this aspect of Unity lately and have found the documentation to be lacking. First there is the inertia member variable. This is effectively the mass when talking about rotation. The mass member has a detailed explanation about how it relates to force and acceleration, but the inertia member does not. Simply explaining that rotationalAcceleration = torque/inertia would be helpful for newcomers. Secondly, when you request the rotational speed from the rigidbody using angularVelocity, you get back a value in degrees/second. This is fine and documented. The problem is the AddTorque function. If you go by angularVelocity, you would expect this to be degrees/sec^2 = torque/inertia. However, it's actually radians/sec^2 = torque/inertia. The result of which is that any torque you apply must first be multiplied with the Deg2Rad constant for it to be predictable, if your own calculations were done using degrees(which is likely since angularVelocity gives deg/sec). And this is *not* mentioned in the documentation for AddTorque.