Askater has rotational inertia 4.2 kg. m2 with his fists held to his chest and 5.7 kg. m2 with his arms outstretched. the skater is spinning at 3.0 rev/s while holding a 2.5-kg weight in each outstretched hand; the weights are 76 cm from his rotation axis. if he pulls his hands in to his chest, so they’re essentially on his ro- tation axis, how fast will he be spinning?

6.13428 rev/s

Explanation:

= Final moment of inertia = 4.2 kgm²

I = Moment of inertia with fists close to chest = 5.7 kgm²

= Initial angular speed = 3 rev/s

= Final angular speed

r = Radius = 76 cm

m = Mass = 2.5 kg

Moment of inertia of the skater is given by

In this system the angular momentum is conserved

The rotational speed will be 6.13428 rev/s

the part of the wave he is travelling on is the crest

be subject to a force andchange its motion