Newton's Second Law of Motion

For Translational Motion
Newton's second law of motion states when a net external force &Sigma F acts on an object with mass of m, the acceleration is inversely proportional to the mass and directly proportional to the net force. The unit for force is Newton (N), or kg · m / s². The equation is shown below:

For Rotational Motion
Newton's second law can be converted into another form to be used for rigid objects in rotational motion. Since tangential acceleration is concerned, the mass of a rigid object times tangential acceleration is the tangential force. In addition, torque is the product of tangential force and the radius of the circular path. Together through substitution, the net external torque is equal to:

In this equation, Σmr² is the moment of inertia, with the symbol I. Therefore, the above equation is expressed in turns of moment of inertia:

Note that angular acceleration must be expressed in terms of rad per second squared.

References and Further Readings

• Cutnell JD,Johnson KW. 2000. Physics. 5th Ed.. (NY): John Wiley & Sons. 1064 p.