I on this problem about angular speed.

AI Thread Summary
To solve the problem of a child jumping onto a rotating disk, apply the conservation of angular momentum. The initial angular momentum of the disk must equal the final angular momentum of the disk-child system. The moment of inertia for the disk can be calculated using the formula 0.25 * m * r^2. By determining the angular momentum of the child at the disk's radius and setting it equal to the total angular momentum after the jump, the new angular speed can be calculated. Understanding these principles is crucial for finding the solution.
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A 22 kg child jumps onto the rim of a 110 kg rotating disk of radius 2.9 m. If the angular speed of the disk before the child's jump was 2.1 rad/s what is the angular speed of the disk-child system?


I got no idea how to start this problem or what formula to use. please help me solve this problem before the day is over. thank you
 
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well the child jumping seems just too much.well anyways i assume that there is suffciient friction between the tyres and teh child(i assume him as a point mass :eek:)

just apply conservation of angular momentum about the centre of the disk.
since all forces torque are internal
 
Look up the definition of angular momentum and moment of inertia.

What is the angular momentum of the child at the radius of the roundabout?

Since angular momentum is conserved what has to happen to the momentum of the roundabout to provide the new angular momentum of the child?

ps. Unless I have missed something, you have to know that the moment of inertia of a flat disk = 0.25 * m * r^2
 
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