A skater on ice with arms extended and one leg out spins at 3 rev/s. After he draws his arms and the leg in, his moment of inertia is reduced to 1/2. What is his new angular speed

The new angular speed is

Explanation:

From the  question we are told that

      The angular velocity of the spin is  

       The  original moment of inertia is  

        The new moment of inertia is      

Generally angular momentum is mathematically represented as

Now according to the law of conservation of momentum, the initial momentum is equal to the final momentum hence the angular momentum is constant so

=>      

where w is the new angular speed  

  So  

=>        

=>        

no. dot product   =0 when vecs at right angles

grav forces affect all objects magnetic forces affect magnetic objects and electric currents