Angular momentum sliding beam

In summary, a 156 kg uniform beam slides down the ice at 9 m/s before a man of mass 88 kg grabs onto one end and spins down with the beam. The y coordinate of the center of mass before the collision, the magnitude of the angular momentum just before the collision, the moment of inertia after the collision, angular velocity after the collision, and the linear speed of the center of mass after the collision are all being asked for. The moment of inertia of the beam is causing a problem when trying to solve the problem.
  • #1
tri5
11
0

Homework Statement


A uniform beam with mass M = 156 kg and length L = 2.3 m slides broadside down along the ice at a speed of v0 = 9 m/s. A man of mass 88 kg, who is initially at rest grabs one end of the beam as it goes past and hangs on as the beam and man go spinning down the ice.

Note: You can assume frictionless motion and the moment of inertia for the man about a vertical axis through his center of mass is negliable. Use the coordinate system shown in the picture, with the origin located at the initial position of the man and the z axis pointed out of the plane.
1)
What is the y coordinate of the center of mass of the system before the collision?
2)
What is the magnitude of the angular momentum of the man + beam system about its center of mass just before the collision?
3)
After the collision, what is the moment of inertia of the man + beam system about an axis perpendicular to the ice through the center of mass of the system?
4)
After the collision, at what angular velocity does the system rotate about its center of mass?
5)
After the collision, what is the linear speed of the center of mass of the system?

Homework Equations


in attachment

The Attempt at a Solution


see attachment
I am having a problem with question number 3. I don't know how to calculate the moment of inertia of the beam. I have used the formula for the moment of inertia of a rod about the center of mass and then using the parallel axis theorem, but the answer is deemed incorrect by the automated homework system. Should I try to treat the beam as a point particle(so then to calculate its moment of inertia I would use mr^2) or some other shape. I know to treat the man as a point particle when calculating its moment of inertia.
 

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  • #2
tri5 said:
I have used the formula for the moment of inertia of a rod about the center of mass and then using the parallel axis theorem, but the answer is deemed incorrect by the automated homework system.

Did you include the moment of inertia of the man? Though it is negligible about an axis passing through him, it is not so when the axis is different ( as in part 3).
 

1. What is angular momentum sliding beam?

Angular momentum sliding beam is a concept in physics that describes the rotational motion of a beam or rod that is sliding or moving along a surface. It is a combination of angular momentum and linear momentum.

2. How is angular momentum sliding beam calculated?

The angular momentum sliding beam is calculated by multiplying the mass of the beam by its velocity and the distance of the beam from the rotational axis.

3. What is the conservation of angular momentum in sliding beams?

The conservation of angular momentum in sliding beams refers to the principle that states that the total angular momentum of a system remains constant as long as there is no external torque acting on the system. This means that the angular momentum of the sliding beam will remain constant unless an external force or torque is applied to it.

4. How does friction affect the angular momentum of a sliding beam?

Friction can affect the angular momentum of a sliding beam by creating a torque that opposes the motion of the beam. This can cause a decrease in the angular momentum of the beam and can also result in the beam coming to a stop.

5. What are some real-life examples of angular momentum sliding beams?

One example of angular momentum sliding beam is a spinning top. As the top slides along a surface, its angular momentum remains constant as long as there is no external force or torque acting on it. Another example is a sliding beam on a roller coaster, where the beam's angular momentum changes as it moves along the track due to changes in its velocity and distance from the rotational axis.

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