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Torque is a concept in physics, often represented by the letter tau, that describes a certain type of force. Specifically, torque refers to the tendency of a force to cause a body to rotate around a central axis. The SI unit for torque is newton meters. Keep reading; we promise to leave your head spinning with facts about torque.
By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on Torque.
ROTATIONAL ANALOG OF FORCE
In linear motion, force can cause an object to accelerate in a particular direction. Torque is called the rotational analog of force because it causes angular acceleration. Instead of simply moving in one direction, an object rotates around its axis when torque is applied.
FORCE VECTOR AND POSITION VECTOR
Force causes an object to accelerate. Torque causes angular acceleration. Torque may be calculated by determining the product of two vectors: the force vector and the position vector. The force vector is the magnitude and direction of an applied force. The position vector is the vector that joins the point of interest on a body and the point on the body where force is applied. In other words, Torque = rFsin𝛩, where theta is the degree measure of the angle between the r and F vectors.
TIME DERIVATIVE OF ANGULAR MOMENTUM
Angular momentum is a property of a rotating object determined by the product of moment of inertia and angular velocity. Moment of inertia refers to a body’s tendency to resist angular acceleration, and is the rotational analog of mass. The time derivative of a function refers to the rate of change of the function with respect to time. Torque, then, is the rate of change in angular momentum with respect to time.
RELATION TO THE MAGNETIC DIPOLE MOMENT
Torque applies to magnetic force as well as mechanical force. When a current passes through loops in a magnetic field, the magnetic field exerts torque on the loops. The flow of electric charge around a loop is called a magnetic dipole, and the magnitude of a magnetic dipole is known as its dipole moment. When defined as a vector, the dipole moment multiplied by the strength of the external magnetic field equals the torque operating on the dipole. To calculate the torque operating on a current-carrying loop in a magnetic field, one must multiply current by number of loops in the turn, area of the loops, the strength of the magnetic field, and the sine of the angle of the loop relative to the field.
WORK AND POWER
Torque performs a certain amount of work, or energy transfer, on a system. The work done by torque can be calculated by multiplying torque and the angular displacement of the object being rotated. Power, simply the rate of change of work with respect to time, can in turn be calculated by multiplying torque and angular velocity.
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Quizbowl is about learning, not rote memorization, so we encourage you to use this as a springboard for further reading rather than as an endpoint. Here are a few things to check out:
Torque helps explain the operation of a torsion balance; a device famously used by Henry Cavendish.
Archimedes may have been the first to discover the unique applications of torque.
Understanding torque can come in handy in a fight!
The Induction Motor may not be a household name, but it should be. So many of our modern comforts are dependent on its ability to convert electrical current to torque!
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