Need help understanding a rotational motion physics concept. What exactly is a net torque?

My physics notes say that an object will remain in "a state of uniform motion unless acted on by a net torque." Does this mean that unless something stops an object from rotating, it will keep rotating forever? Is a net torque always equal to zero and will it keep an object at rest? Is a net torque a balanced force?Need help understanding a rotational motion physics concept. What exactly is a net torque?In answer to UR first question, a clarification is necessary: A rotating object may be: 1) spinning at constant speed (called "uniform motion") or 2) changing speed {either accelerating or decelerating angularly}.



If an object is spinning at CONSTANT speed it will do so forever IF no NET torque acts on it. As this is the same concept as is true for linear motion of objects when no NET force acts on them - it is part of Newton's 1st Law.



In order to have an object start spinning from rest OR have a spinning object CHANGE speed, a NET torque must act on the object.



A NET torque is never = 0 by definition. The fact that a NET torque exists means that the SUM of all torques that act on an object %26gt; 0. Therefore it is an UN-balanced torque.



Another physics name for "torque" is "moment". Both are identical in meaning and have as SI units: "meter-Newtons" or m-N.



{I always put the m before the N for torques/moments because vice-versa: "Newton-Meters" or N-m can be confused with the energy unit: Joules which is N-m also}Need help understanding a rotational motion physics concept. What exactly is a net torque?Hello Chevita127, yes unless an external force comes into play the body being in uniform motion would ever continue that motion.

In case of linear motion we use force. But in case of rotational motion we use moment of the force which is otherwise known as torque.

If we keep a magnetic needle in a region where two magnetic field interact at right angles to each other then the torque acting will become equal and opposite and hence the needle gets settled in an equilibrium deflected position.

Torque is a vector whose direction will be normal to the plane containing the force and the radius vector.Need help understanding a rotational motion physics concept. What exactly is a net torque?Torque is nothing more than a rotational twisting equivalent of a force. I will explain it later.



Before jumping to understand the principles of rotational motion, you should first be sure you fully understand the laws of pure translational motion. There are many analogies between the two, and there are ways in which the concepts relate.



Also, net is nothing more than total. As in a vector sum of all the influences (forces or torques depending on which you are interested in).



"Does this mean that unless something stops an object from rotating, it will keep rotating forever?"



Yes indeed. This is the rotational version of Newton's first law and the principle of inertia. Don't let frictional effects deceive you. Friction is a force/torque, just like a human push/pull or gravity is a force/can be a torque if applied correct.



"Is a net torque always equal to zero and will it keep an object at rest?"



No, it is not always equal to zero, otherwise I wouldn't be able to type this message. It is only zero, if the target body is either not rotating, or rotating at a constant speed, constant axis, constant direction (i.e. constant angular velocity).



A net torque of zero is necessary for a body to remain rotationally at rest. That is true. However, just because a net torque was zero, does not mean the body will be brought to rest. If a body spins free of friction with zero net torque, it will rotate forever around the same axis, at the same speed, in the same direction.