Torque

Definition

Torque is a measure of the rotational force that causes an object to rotate about an axis, fulcrum, or pivot. It is the product of the force applied and the perpendicular distance between the line of action of the force and the axis of rotation. Torque is a crucial concept in the study of rotational motion and equilibrium.

5 Must Know Facts For Your Next Test

1. Torque is the cross product of the position vector and the force vector, which gives the magnitude and direction of the rotational force.
2. The SI unit of torque is Newton-meter (N⋅m), which is the product of force (N) and distance (m).
3. Torque can be used to calculate the center of mass and moments of inertia of an object, which are important in determining its rotational dynamics.
4. The direction of the torque vector is determined by the right-hand rule, which follows the direction of the rotation caused by the force.
5. Torque is a vector quantity, meaning it has both magnitude and direction, and it can be positive or negative depending on the direction of rotation.

Review Questions

• Explain how the concept of torque is related to the cross product in the context of 2.4 The Cross Product.
  • The cross product is a key mathematical operation that is used to calculate the torque acting on an object. The cross product of the position vector and the force vector gives the magnitude and direction of the torque. Specifically, the torque vector is defined as the cross product of the position vector and the force vector, $\vec{\tau} = \vec{r} \times \vec{F}$. This relationship allows us to determine the rotational effect of a force acting on an object, which is essential for understanding rotational motion and equilibrium.
• Describe how the concept of torque is used in the calculation of centers of mass and moments of inertia, as discussed in 5.6 Calculating Centers of Mass and Moments of Inertia.
  • Torque is a crucial concept in the calculation of centers of mass and moments of inertia. The center of mass of an object is the point at which the object's weight can be considered to be concentrated, and it is determined by the distribution of mass within the object. Torque is used to find the center of mass by balancing the torques about a chosen axis. Similarly, the moment of inertia of an object, which is a measure of an object's resistance to rotational acceleration, is also calculated using the concept of torque. The moment of inertia depends on the distribution of mass within the object, and torque is used to determine this distribution and calculate the moment of inertia.
• Evaluate the importance of understanding the concept of torque in the context of rotational motion and equilibrium, and explain how it relates to the topics of 2.4 The Cross Product and 5.6 Calculating Centers of Mass and Moments of Inertia.
  • Understanding the concept of torque is essential for studying rotational motion and equilibrium, as it is the key to understanding the rotational dynamics of objects. Torque is the rotational analog of force, and it determines how an object will rotate about a given axis. In the context of 2.4 The Cross Product, the cross product is used to calculate the torque acting on an object, which is crucial for understanding rotational motion. Additionally, in the context of 5.6 Calculating Centers of Mass and Moments of Inertia, the concept of torque is used to determine the distribution of mass within an object, which is necessary for calculating the center of mass and moments of inertia. These quantities, in turn, are essential for understanding the rotational dynamics of objects and predicting their behavior. Therefore, a deep understanding of the concept of torque is fundamental for success in these topics and in the broader study of rotational motion and equilibrium.

Related terms

Moment: The moment of a force is the product of the force and the perpendicular distance from the axis of rotation to the line of action of the force. Torque is a type of moment.

Angular Momentum:

Angular momentum is the rotational analog of linear momentum, and it is the product of an object's moment of inertia and its angular velocity. Torque is the rate of change of angular momentum.

Equilibrium:

Equilibrium is a state of balance where the net force and net torque acting on an object are both zero. Torque is a key factor in determining the equilibrium of a rotational system.