drift velocity

Examples of drift velocity in the following topics:

• A Microscopic View: Drift Speed

  • The drift velocity is the average velocity that a particle achieves due to an electric field.
  • The drift velocity vdis the average velocity of the free charges after applying the field.
  • The drift velocity is quite small, since there are so many free charges.
  • The average velocity of the free charges is called the drift velocity and is in the direction opposite to the electric field for electrons.
  • Relate the drift velocity with the velocity of free charges in conductors

• Magnetic Force on a Current-Carrying Conductor

  • The force (F) a magnetic field (B) exerts on an individual charge (q) traveling at drift velocity vd is:

• Water Waves

  • As the wave amplitude (height) increases, the particle paths no longer form closed orbits; rather, after the passage of each crest, particles are displaced slightly from their previous positions, a phenomenon known as Stokes drift.
  • The deep-water group velocity is half the phase velocity.
  • In shallow water for wavelengths larger than about twenty times the water depth (as often found near the coast), the group velocity is equal to the phase velocity.
  • We see a wave propagating in the direction of the phase velocity.
  • The wave can be thought to be made up of planes orthogonal to the direction of the phase velocity.

• Genetic Drift

  • Genetic drift is the change in allele frequencies of a population due to random chance events, such as natural disasters.
  • Genetic drift is the converse of natural selection.
  • Small populations are more susceptible to the forces of genetic drift.
  • Thus even while genetic drift is a random, directionless process, it acts to eliminate genetic variation over time.
  • Genetic drift in a population can lead to the elimination of an allele from that population by chance.

• Relative Velocity

  • Relative velocity is the velocity of an object B measured with respect to the velocity of another object A, denoted as $v_{BA}$.
  • Relative velocity is the velocity of an object B, in the rest frame of another object A.
  • Is the velocity of the fly, $u$, the actual velocity of the fly?
  • No, because what you measured was the velocity of the fly relative to the velocity of the boat.
  • The velocity that you observe the man walking in will be the same velocity that he would be walking in if you both were on land.

• Tangent and Velocity Problems

  • Velocity is defined as rate of change of displacement.
  • The average velocity becomes instantaneous velocity at time t.
  • Instantaneous velocity is always tangential to trajectory.
  • Slope of tangent of position or displacement time graph is instantaneous velocity and its slope of chord is average velocity.
  • Its slope is the velocity at that point.

• Instananeous Velocity: A Graphical Interpretation

  • Instantaneous velocity is the velocity of an object at a single point in time and space as calculated by the slope of the tangent line.
  • Typically, motion is not with constant velocity nor speed.
  • However, changing velocity it is not as straightforward.
  • Since our velocity is constantly changing, we can estimate velocity in different ways.
  • Motion is often observed with changing velocity.

• Velocity and Duration of Muscle Contraction

  • The shortening velocity affects the amount of force generated by a muscle.
  • The force-velocity relationship in muscle relates the speed at which a muscle changes length to the force of this contraction and the resultant power output (force x velocity = power).
  • As velocity increases force and therefore power produced is reduced.
  • Although force increases due to stretching with no velocity zero power is produced.
  • Maximum power is generated at one-third of maximum shortening velocity.

• Relativistic Addition of Velocities

  • A velocity-addition formula is an equation that relates the velocities of moving objects in different reference frames.
  • A velocity-addition formula is an equation that relates the velocities of moving objects in different reference frames.
  • As Galileo Galilei observed in 17th century, if a ship is moving relative to the shore at velocity $v$, and a fly is moving with velocity $u$ as measured on the ship, calculating the velocity of the fly as measured on the shore is what is meant by the addition of the velocities $v$ and $u$.
  • Since this is counter to what Galileo used to add velocities, there needs to be a new velocity addition law.
  • This change isn't noticeable at low velocities but as the velocity increases towards the speed of light it becomes important.

• Addition of Velocities

  • Relative velocities can be found by adding the velocity of the observed object to the velocity of the frame of reference it was measured in.
  • As learned in a previous atom, relative velocity is the velocity of an object as observed from a certain frame of reference.
  • demonstrates the concept of relative velocity.
  • When she throws the snowball forward at a speed of 1.5 m/s, relative to the sled, the velocity of the snowball to the observer is the sum of the velocity of the sled and the velocity of the snowball relative to the sled:
  • The magnitude of the observed velocity from the shore is the square root sum of the squared velocity of the boat and the squared velocity of the river.