Integrated SequencePhysics Chemistry Organic Biology

WikiPremed Resources

Module 2 in the Syllabus

Rotation Cards
Chapter from the Wisebridge Learning System for Physics

Rotation Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Rotation
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Overview of Rotation
In our earlier discussions of mechanics, we have been relying on what physicists call 'the particle model' of a material body. No problem with that, except that now we want to analyze the motion of an extended body in which different parts have relative motion with regard to each other. Unlike a particle, such an extended body can undergo rotation. To first approach the more complex motion of rotation, it is helpful to have recourse to a simplified model system. In rotation, the simplified model system is the rigid body rotating around a fixed axis.

Rotation on the MCAT
Although straightforward rotation problems seem to show up a bit less on the MCAT compared to the rest of classical mechanics, it is still an important topic for MCAT review. Comparison of rolling versus sliding motion has appeared fairly often, and static equilibrium problems involving summation of torque have appeared a few times.

Conceptual Vocabulary
TorqueTorque or moment can informally be thought of as rotational force or angular force which causes a change in rotational motion. It is defined by linear force multiplied by a radius.
RotationA rotation is a movement of an object in a circular motion, around a center for a point, around a line called an axis for a three dimensional object.
Angular momentumThe angular momentum of an object rotating about some reference point is the measure of the extent to which the object will continue to rotate about that point unless acted upon by an external torque.
Angular velocityThe angular velocity specifies the angular speed at which an object is rotating along with the direction in which it is rotating.
Moment of inertiaMoment of inertia is the rotational analog of mass. That is, it is the inertia of a rigid rotating body with respect to its rotation.
Angular displacementAngular displacement of a body is the angle through which a point or line has been rotated in a specified sense about a specified axis.
Rotational energySometimes called angular kinetic energy, the rotational energy is the kinetic energy due to the rotation of an object.
Angular frequencyAngular frequency is a scalar measure of rotation rate. It is the magnitude of the angular velocity.
Angular accelerationAngular acceleration is the rate of change of angular velocity.
Mechanical equilibriumA system is in mechanical equilibrium when the sum of the forces and torques on each particle of the system is zero.
Revolutions per minuteRevolutions per minute is a unit of frequency: the number of full rotations completed in one minute around a fixed axis.
StaticsStatics is the branch of physics concerned with the analysis of loads, ie. forces and torques, on physical systems in static equilibrium.
Rigid bodyA rigid body is an idealization of a solid body of finite size in which deformation is neglected.
GyroscopeA gyroscope is a device based on the principle of conservation of angular momentum. The essence of the device is a spinning wheel on an axle.
RadianOne radian is the angle subtended by an arc length equal to the radius of the circle.
Radian per secondThe radian per second is the SI unit of angular velocity.
CoupleA couple is a system of forces with a resultant moment but no resultant force. Its effect is to create rotation without translation.
PrecessionPrecession refers to a change in the direction of the axis of a rotating object.
PseudovectorA pseudovector (or axial vector) is a quantity that transforms like a vector under a proper rotation, but gains an additional sign flip under an improper rotation.
FlywheelA flywheel is a rotating disk used as a storage device for kinetic energy.
Rigid rotorThe rigid rotor is a mechanical model that is used to explain rotating systems. Three angles are required to orient such an object in space.

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