7. Phase separation in liquid heterogeneous systems
Covers uniform circular motion, explaining constant speed with changing velocity, centripetal acceleration and force, and the tangential velocity, angular velocity, period and frequency. It then moves to centrifugal force as an inertial effect, centrifuges and their types (fixed-angle, swinging-bucket, ultracentrifuges), sedimentation velocity, and finally the physiological effects of inertial forces on the body, including positive, negative and transverse effects, overloading and weightlessness.
Topic 8 of 42 in the MU Sofia syllabus for Physics (Medicine, Year 1). The free AceMed note covers it in 1 section, about 794 words (5 min of reading), with 10 flashcards.
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Introduction
Introduction
Uniform circular motion
Definition:
Uniform circular motion involves an object moving along a circular path with a constant speed.
Despite the constant speed, the velocity of the object changes continuously due to the continuous change in direction.
The acceleration responsible for keeping the object in circular motion is called centripetal acceleration (or radial acceleration).
The force that acts toward the center of the circle, providing this acceleration, is known as the centripetal force.
In uniform circular motion, an object moves along a circular path at a constant speed.
The tangential velocity ($Vt$) is the linear speed of the object along the circle.
The angular velocity ($ω$) measures how quickly the object rotates.
The period ($T$) is the time it takes for the object to complete one full revolution, while the frequency ($f$) is the number of revolutions per unit time.
Key Points:
Speed: Remains constant throughout the circular path.
Velocity: Changes at every instant due to direction change.
Tangential Acceleration: No tangential acceleration (i.e., acceleration along the tangent to the circle).
Radial (Centripetal) Acceleration: Given by :
Centripetal acceleration
Centripetal force is the force that acts on an object moving in a circular path, pulling it toward the center of that circle.
It is essential to keep the object in its circular trajectory.
(m) represents the mass of the object.
(v) is the linear velocity (speed) of the object along the circular path.
(r) denotes the radius of the circular path.
Centrifugal force.
Centrifuge:
A centrifuge is a laboratory device that rotates at high speeds to separate substances based on their density.
It exploits the principle of centrifugal force to achieve this separation.
Common applications include separating blood components, purifying DNA, and analyzing particles in various liquids.
Centrifugal Force:
Centrifugal force is a fictitious force that appears to act outward from the center of rotation when an object moves in a circular path.
It is not a true force but rather an inertial effect due to the object’s tendency to move in a straight line (inertia) while constrained to a curved path
Sedimentation and centrifugation.
Sedimentation is the process of deposition where particles suspended in a fluid settle out and come to rest against a barrier. This occurs due to their motion through the fluid, influenced by various forces such as gravity, centrifugal acceleration, or electromagnetism1. Let’s break it down:
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