A playground merry-go-round has a radius of R = 4.0 m and has a moment of inertia Icm = 7.0 x 10³ kgm² about an axis passing through the center of mass. There is negligible friction about its vertical axis. Two children each of mass m = 25 kg are standing on opposite sides a distance ro= 3.0 m from the central axis. The merry-go-round is initially at rest. A person on the ground applies a constant tangential force of F= 2.5 x10² N at the rim of the merry-go-round for a time At=1.0 x 10¹ s. Lebah R a. What is the magnitude of angular acceleration of the merry-go-round? b. What is the angular speed of the merry-go-round when the person stopped applying the force? c. What is the rotational kinetic energy of the merry-go-round when the person stopped applying the force? d. The two children then walk inward and stop a distance of r1 =1.0 m from the central axis of the merry-go-round. What is the angular velocity of the merry-go- round when the children reach their final position? What is the change in rotational kinetic energy of the merry-go-round when the children reached their final position?
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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