A person holds his outstretched arm at rest in a horizontal position. The mass of the arm is m and its length is 0.740 m.When the person releases his arm, allowing it to drop freely, it begins to rotate about the shoulder joint. Find (a) theinitial angular acceleration of the arm, and (b) the initial linear acceleration of the man’s hand. (Hint: In calculatingthe torque, assume the mass of the arm is concentrated at its midpoint. In calculating the angular acceleration, use themoment of inertia of a uniform rod of length L about one end; I = 13mL2.)
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.
A person holds his outstretched arm at rest in a horizontal position. The mass of the arm is m and its length is 0.740 m.
When the person releases his arm, allowing it to drop freely, it begins to rotate about the shoulder joint. Find (a) the
initial
the torque, assume the mass of the arm is concentrated at its midpoint. In calculating the angular acceleration, use the
moment of inertia of a uniform rod of length L about one end; I = 1
3mL2
.)
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