Keratinocytes are the most common cells in the skin’souter layer. As these approximately circular cells migrateacross a wound during the healing process, they roll in a waythat reduces the frictional forces impeding their motion.(a) Given a cell body diameter of 1.00 x 10-5 m (10 μm),what minimum angular speed would be required to producethe observed linear speed of 1.67 x 10-7 m/s (10 μm/min)?(b) How many complete revolutions would be required forthe cell to roll a distance of 5.00 x 10-3 m? (Because of slippingas the cells roll, averages of observed angular speeds andthe number of complete revolutions are about three timesthese minimum values.)
Angular Momentum
The momentum of an object is given by multiplying its mass and velocity. Momentum is a property of any object that moves with mass. The only difference between angular momentum and linear momentum is that angular momentum deals with moving or spinning objects. A moving particle's linear momentum can be thought of as a measure of its linear motion. The force is proportional to the rate of change of linear momentum. Angular momentum is always directly proportional to mass. In rotational motion, the concept of angular momentum is often used. Since it is a conserved quantity—the total angular momentum of a closed system remains constant—it is a significant quantity in physics. To understand the concept of angular momentum first we need to understand a rigid body and its movement, a position vector that is used to specify the position of particles in space. A rigid body possesses motion it may be linear or rotational. Rotational motion plays important role in angular momentum.
Moment of a Force
The idea of moments is an important concept in physics. It arises from the fact that distance often plays an important part in the interaction of, or in determining the impact of forces on bodies. Moments are often described by their order [first, second, or higher order] based on the power to which the distance has to be raised to understand the phenomenon. Of particular note are the second-order moment of mass (Moment of Inertia) and moments of force.
Keratinocytes are the most common cells in the skin’s
outer layer. As these approximately circular cells migrate
across a wound during the healing process, they roll in a way
that reduces the frictional forces impeding their motion.
(a) Given a cell body diameter of 1.00 x 10-5 m (10 μm),
what minimum angular speed would be required to produce
the observed linear speed of 1.67 x 10-7 m/s (10 μm/min)?
(b) How many complete revolutions would be required for
the cell to roll a distance of 5.00 x 10-3 m? (Because of slipping
as the cells roll, averages of observed angular speeds and
the number of complete revolutions are about three times
these minimum values.)
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