Question

figures show the two different spinning poses of a ballet dancer.
(a) In which spinning pose the ballet dancer have more angular speed.
(b) state the principle used by the ballet dancer to increase his angular speed. ​

Answer 1

1. The 2nd posture of the ballet dancer will get her a greater angular velocity.

But why??

• Whenever the ballet dancer folds her arms and brings them towards the centre of the body the moment of inertia (along the axis of rotation) decreases as a result of which, the angular velocity increases.

2. This phenomenon is based on the principle of CONSERVATION OF ANGULAR MOMENTUM.

But why ??

• Basically, whenever the ballet dancer is rotating on a fixed axis, she is not experiencing any external torque. Hence, we can say that her angular momentum is constant.

$\therefore\sum(\tau)=0\\\\\implies\dfrac{dL}{dt}=0\\\\\implies L=constant$

$\star$ Hope It Helps.

Answer 2

a) Yes, whenever the moment of inertia is less, the angular velocity is more . So dancer has to put the hands near her body.

b) Principle is Conservation of Angular Momentum

$I \times \omega = constant$