11P06

 11P06 System of Particles and Rotational Motion

Person on a rotating platform

Conservation of Angular Momentum 

Defying gravity? with Angular Momentum Concepts

(NCERT Page no.156, Vol 1, XI Physics Text book)

Defying gravity? with Angular Momentum Concepts

(NCERT Page no.156, Vol 1, XI Physics Text book)

Person on a turn table with Rotating wheel.

Explanation for above demonstration:

Person with rotating wheel on a turn table, Conservation of Angular Momentum in absence of external torque. In the absence of external forces, linear Momentum of a system remains same or conserved e.g when bullet is fired the gun is recoiled backwards to achieve the initial Momentum zero. Mgun Vgun + Mbullet Vbullet = 0, Recoil speed of gun Vgun = - Vbullet Mbullet / Mgun Notice the negative sign so the gun will go opposite to the bullet. Similarly in the Rotational motion, in the absence of external torque, Angular Momentum is conserved in a system or remains same. When the wheel is rotating in one direction, the turn table rotates in the opposite direction to conserve Angular Momentum.

Rolling motion is a combination of Rotational motion and Linear motion. Three different speeds are there in a wheel. The center of mass of the wheel is moving with the same speed as the car itself. However the top point of the wheel is moving at twice the speed of car and the lowest point of the wheel in contact with the road is at zero speed, momentarily stationary.