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# Tag Archives: angular

## Physics of Diving

When a high diver in a swimming event springs from the board and “tucks in”, a rapid spin **result**. Why is this?

Answer: This is the consequence of **conservation** of **angular** momentum.

The **angular** momentum of a **body** is the **product** of Moment of inertia (*A measure of rotational inertia and it depends on the mass as well as distribution of mass about the axis of rotation. Farther the masses, greater will be the rotational inertia*) and the

**angular**

**velocity**(The speed of

**rotation**)

The **angular** momentum of a **body** remains unchanged in the **absence** of any external torque.

When the diver dives, he is giving his **body** a turning and takes off with his limbs stretched. In the stretched **position**, the **moment of inertia** is more. When he “tucks in”, the **moment of inertia** decreases. But since this happens without any external torque, it would **result** in an increase in **angular** **velocity** so as to keep the **angular** momentum constant.

## Conservation of Angular Momentum and Kinetic Energy

Imagine a rod 2 meters long fixed at its center, 2 identical masses are placed 0.5 meters away on opposite sides , as the rod spins they slide towards the edges , according to the formula k.E.=0.5*I*ω^{2} the kinetic energy decreases , but since its a closed system why does the kinetic energy decrease ?

**Answer**:

The decrease in KE accounted by the work done in displacing the masses

## Dispersion

Ashish Asks:

IN A PRISM DISPERSION OCCURS BUT NOT IN A GLASS SLAB PLEASE EXPLAIN ME CLEARLY WHY IN THE GLASS SLAB THE DISPERSION DOES NOT TAKES PLACE.

Answer: In a glass slab, the opposite sides are parallel. Though splitting up of light takes place inside the glass slab, the emergent rays are parallel to each other and enter simultaneously without any angular separation. But, in the case of a glass prism, the angular separation produced to the component colours due to refraction at the first face is further enhanced at the second face. Thus the angular separation between the emergent colours enables the viewer to see the colours separately and thus the dispersion is observed.

## Question from Rotational Dynamics

**Dyana** Asked:

A small rubber wheel is used to drive a large pottery wheel. The two wheels are mounted so that their circular edges touch. The small wheel has a radius of 3.5 cm and accelerates at the rate of 7.9 rad/s^2, and it is in contact with the pottery wheel (radius 23.0 cm) without slipping.

a)Calculate the angular acceleration of the pottery wheel

b)Calculate the time it takes the pottery wheel to reach its required speed of 64 rpm

**Students and teacher visitors are requested to respond**