curious physics student wonders if he left his physics book on the ground and jumped onto the merry-go-round, and started walking, will he ever move away from the physics book, assume he is less than half its mass? a. No, the merry-go-round will have angular momentum in one direction and he in the other, they will cancel and he’ll stay right above the book. b. No, because the initial angular momentum is zero, so the final must be zero too, causing his angular velocity to be zero, so he’ll stay right above the book. c. Yes, angular momentum is not conserved so he’ll move around away from the book. d. Yes, because his moment of inertia is smaller than the merry-go-round’s, so his angular velocity will be bigger, so he’ll move around away from the book.
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.
3. At a dilapidated playground, people have stolen the support bar to a merry-go-round leaving a flat
disk that can rotate freely. While pondering conservation of
student wonders if he left his physics book on the ground and jumped onto the merry-go-round, and
started walking, will he ever move away from the physics book, assume he is less than half its mass?
a. No, the merry-go-round will have angular momentum in one direction and he in the other, they
will cancel and he’ll stay right above the book.
b. No, because the initial angular momentum is zero, so the final must be zero too, causing his
angular velocity to be zero, so he’ll stay right above the book.
c. Yes, angular momentum is not conserved so he’ll move around away from the book.
d. Yes, because his moment of inertia is smaller than the merry-go-round’s, so his angular velocity
will be bigger, so he’ll move around away from the book.
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