One of the more challenging elements in pairs figure skating competition is the "death spiral" (see the figure below), in which the female figure skater, balanced on one skate, is spun in a circle by the male skater. The axis of rotation of the pair is vertical and through the toe of the skate on the male skater's leg that is bent backward, the toe being planted into the ice. During the one-armed maneuver first developed in the 1940s, the outstretched arm of the male skater must apply a large force to support a significant fraction of the female skater's weight and also to provide her centripetal acceleration. This force represents a danger to the structure of the wrist of the male skater. (a) Modeling the female skater, of mass 54.0 kg, as a particle, and assuming that the combined length of the two outstretched arms is 120 cm and that arms make an angle of 45.0° with the horizontal, what is the magnitude of the force (in N) exerted by the male skater's wrist if each turn is completed in 2.00 s? N (b) How does this force compare to that on one wrist of a 70.0 kg person preparing to do chin-ups by hanging from an exercise bar from the wrists? Fmale skater's wrist F one wrist of 70.0 kg person
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.
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