A disc-shaped grindstone of mass 3.0 kg and radius 8.0 cm is spinning at 600 revolutions/min. The moment of inertia of a disc rotating about its center is given by I = }MR² The power is shut off by the operator and to slow it down, she sharpens a 3 kg axe by holding it against the grindstone until it stops 10 s later. Assuming the angular acceleration is constant while the grindstone is slowing down, find the magnitude of the net frictional torque exerted by the axe on the grindstone. 0.060 Nm 603.17 Nm 0.576 Nm 5760 Nm 0.121 Nm
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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