2. A man of mass 80.0 kg is standing at the center of a rotating disk of mass 20 kg and radius 65 cm with his arms at his sides. Consider his body (including his head and legs) as a cylinder of mass 68.0 kg, 13.0 cm in radius and 1.70 m high and each arm is a thin rod of mass 6.00 kg and length 58.0 cm. (a) =) If the angular velocity of the system is 7.25 rad/s when his arms are parallel to his sides, find the angular velocity of the system when he raises his arms perpendicular to his body as shown in figure. (b) es) Calculate the amount of force perpendicular to the edge of the disk required to produce 15 revs from rest at 5 sec when his arms are parallel to his sides.
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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