Learning Goal: To understand how to use conservation of angular momentum to solve problems involving collisions of rotating bodies. Consider a turntable to be a circular disk of moment of inertia It rotating at a constant angular velocity wi (note that angular velocities use the Greek letter omega and not double-u) around an axis through the center and perpendicular to the plane of the disk (the disk's "primary axis of symmetry") as shown in (Figure 1). The axis of the disk is vertical and the disk is supported by frictionless bearings. The motor of the turntable is off, so there is no external torque being applied to the axis. Another disk (a record) is dropped onto the first such that it lands coaxially (the axes coincide). The moment of inertia of the record is Ir. The initial angular velocity of the second disk is zero. There is friction between the two disks. After this "rotational collision," the disks will eventually rotate Figure < 1 of 1 Part A What is the final angular velocity, wf, of the two disks? Express wf (omega subscript f) in terms of It, Ir, and wi (omega subscript i). View Available Hint(s) ΠΫΠΙ ΑΣΦ Submit Part B Because of friction, rotational kinetic energy is not conserved while the disks' surfaces slip over each other. What i s the final rotational kinetic energy, Kr, of the two spinning disks? Express the final kinetic energy in terms of It, Ir, and the initial kinetic energy K₁ of the two-disk system. No angular velocities should appear in your answer. ▸ View Available Hint(s) K₁ = Submit [ΕΙ ΑΣΦ 3 ?
Learning Goal: To understand how to use conservation of angular momentum to solve problems involving collisions of rotating bodies. Consider a turntable to be a circular disk of moment of inertia It rotating at a constant angular velocity wi (note that angular velocities use the Greek letter omega and not double-u) around an axis through the center and perpendicular to the plane of the disk (the disk's "primary axis of symmetry") as shown in (Figure 1). The axis of the disk is vertical and the disk is supported by frictionless bearings. The motor of the turntable is off, so there is no external torque being applied to the axis. Another disk (a record) is dropped onto the first such that it lands coaxially (the axes coincide). The moment of inertia of the record is Ir. The initial angular velocity of the second disk is zero. There is friction between the two disks. After this "rotational collision," the disks will eventually rotate Figure < 1 of 1 Part A What is the final angular velocity, wf, of the two disks? Express wf (omega subscript f) in terms of It, Ir, and wi (omega subscript i). View Available Hint(s) ΠΫΠΙ ΑΣΦ Submit Part B Because of friction, rotational kinetic energy is not conserved while the disks' surfaces slip over each other. What i s the final rotational kinetic energy, Kr, of the two spinning disks? Express the final kinetic energy in terms of It, Ir, and the initial kinetic energy K₁ of the two-disk system. No angular velocities should appear in your answer. ▸ View Available Hint(s) K₁ = Submit [ΕΙ ΑΣΦ 3 ?
University Physics Volume 1
18th Edition
ISBN:9781938168277
Author:William Moebs, Samuel J. Ling, Jeff Sanny
Publisher:William Moebs, Samuel J. Ling, Jeff Sanny
Chapter11: Angular Momentum
Section: Chapter Questions
Problem 59P: A bug of mass 0.020 kg is at rest on the edge of a solid cylindrical disk (M=0.10kg,R=0.10m)...
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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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Help with this would be great, thanks!
Transcribed Image Text:Learning Goal:
To understand how to use conservation of angular
momentum to solve problems involving collisions of rotating
bodies.
Consider a turntable to be a circular disk of moment of inertia
It rotating at a constant angular velocity w; (note that
angular velocities use the Greek letter omega and not
double-u) around an axis through the center and
perpendicular to the plane of the disk (the disk's "primary
axis of symmetry") as shown in (Figure 1). The axis of the
disk is vertical and the disk is supported by frictionless
bearings. The motor of the turntable is off, so there is no
external torque being applied to the axis.
Another disk (a record) is dropped onto the first such that it
lands coaxially (the axes coincide). The moment of inertia of
the record is Ir. The initial angular velocity of the second
disk is zero.
There is friction between the two disks.
After this "rotational collision," the disks will eventually rotate
Figure
k
4
1 of 1
Part A
What is the final angular velocity, wf, of the two disks?
Express wf (omega subscript f) in terms of It, Ir, and w; (omega subscript i).
► View Available Hint(s)
Wf =
Submit
Part B
V—| ΑΣΦ
Because of friction, rotational kinetic energy is not conserved while the disks' surfaces slip over each other. What is the final rotational kinetic
energy, Kf, of the two spinning disks?
Kf =
Express the final kinetic energy in terms of It, Ir, and the initial kinetic energy K; of the two-disk system. No angular velocities should
appear in your answer.
► View Available Hint(s)
Submit
?
πV—| ΑΣΦ
?
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