# Rolling, Torque, and Angular Momentum

• ranjaxt2012
It is possible that it is not a homework question, but it is still not really appropriate for the general forum. The discussion about whether it is appropriate belongs in the "Feedback/Suggestions" forum, so I am moving this thread to there.
ranjaxt2012
A girl of mass 28.1 kg stands on the rim of a frictionless merry-go-round of radius 1.58 m and rotational inertia 433 kg·m2 that is not moving. She throws a rock of mass 670 g horizontally in a direction that is tangent to the outer edge of the merry-go-round. The speed of the rock, relative to the ground, is 7.78 m/s. Afterward, what are (a) the angular speed of the merry-go-round and (b) the linear speed of the girl?

Mass M = 28.1 kg
R-Inertia = 433 Kg.m2
mass of rock = 670g = .67 kg (tangent to merry-go-round)
speed of rock = 7.78 m.s
now is the angular speed ω of merry-go-round = ?
we know ω = L/Inertia or (m.r.v)/inertia.
Now what is velocity of the system? is it 7.78?

if yes then

ω = [(28.1+.67)*1.58*7.78)]/433 ≈ 0.81674 rad/sec

is linear speed of the girl = 0.816748*r

Hi ranjaxt2012! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

This sounds like a homework question, so should really be posted in the homework sub-forum.

Last edited by a moderator:

## 1. What is the difference between rolling and sliding friction?

Rolling friction occurs when an object rolls over a surface, such as a wheel on the ground. Sliding friction occurs when an object slides over a surface, such as a book being dragged across a table. Rolling friction is typically lower than sliding friction because the object is in contact with the surface at fewer points.

## 2. How is torque different from force?

Torque is a measure of the rotational force applied to an object, while force is a measure of the linear force applied to an object. Torque involves an object's moment of inertia and distance from the axis of rotation, while force only considers the mass and acceleration of an object.

## 3. What factors affect the magnitude of angular momentum?

The magnitude of angular momentum is affected by an object's moment of inertia, angular velocity, and the distance from the axis of rotation. It also depends on whether the object is rotating about a fixed or moving axis.

## 4. How does angular momentum relate to conservation of momentum?

Angular momentum is the product of an object's moment of inertia and angular velocity. In a closed system, where no external forces act on the system, angular momentum is conserved. This means that the total angular momentum of the system remains constant, even if individual objects within the system experience changes in their angular momentum.

## 5. What are some real-world applications of torque and angular momentum?

Some real-world applications of torque and angular momentum include the rotation of bicycle wheels, the spinning of a top, the flight of a Frisbee, and the movement of a satellite in orbit around a planet. These principles also play a role in the functioning of machines such as car engines, turbines, and gears.

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