A circular bird feeder 19 cm in radius has rotational inertia 0.12kg·m2. The feeder is suspended horizontally by a thin wire through the middle, and is spinning slowly
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.
A circular bird feeder 19 cm in radius has rotational inertia 0.12kg·m2. The feeder is suspended horizontally by a thin wire through the middle, and is spinning slowly at 6.1 rpm. A 140 g bird lands on the rim of the feeder, coming in tangent to the rim at 1.1 m/s in a direction opposite the feeder’s rotation. Assume the feeder-bird system is isolated; no pFBD or IST is required for this problem. Please put your answers in terms of the variables listed.
Variables:
R-radius of feeder
I0-Feeder inertia
w0-initial
m-bird mass
v0-bird initial speed
Lbird-bird intitial
Iafter-system final inertia
wf-final angular velocity
q. Treat the bird as a point-particle, and define the feeder’s initial rotation direction to be positive. Write an expression in terms of given variables for the bird’s angular momentum immediately before contact with the feeder about the feeder’s axis of rotation Lbird in terms of the variables above.
Trending now
This is a popular solution!
Step by step
Solved in 3 steps with 3 images
