# Rigid body rototion with 4 force

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Hello! I'm try a car simulator game. I have a problem: I have a rectangle, at 4 corners influence 4 force. How can I rotate the rectangle whith this forces?

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Suppose you dont have any appearent point of rotation, then the body will rotation about it's center of mass. Do a torque at the CM for all forces, sum it up. Note that

Torque = I * Alpha;

Where I is the moment of inertia of the block and
Alpha is the angular acceleration.

Once you have the angular acceleration, you can calculate the angle by integrating the expression twice.

To actually carry out the rotation and display it on the screen, you will need to run the mesh thru a rotational transformation, the one that is defined by the Rotation Matrix.

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f@bo,

In general, forces applied to a rigid body cause a torque, which results in a change in angular momentum according to the Euler equation of rotational rigid body motion. Basically, you need to integrate the rotational equation of motion in a manner similar to the integration of the translational equation of motion.

Your question is general, and so I give you a general reference. I suggest you search the forum archives since the topic of car simulation is very common. You will find many useful discussions in the archives. Second, I suggest you read an introduction to rigid body dynamics simulation. You can find one such introduction here:

An Introduction to Physically Based Modeling: Rigid Body Simulation I—Unconstrained Rigid Body Dynamics

I hope this helps!

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