Angular momentum and its conservation
- The Sun rotates around its centre once in 27 days. What will be the period of revolution if the Sun were to expand to twice its present radius without any external influence? Assume the Sun to be a sphere of uniform density. Answer: 4. 108 days Key idea: no external torque, so angular momentum L=Iω is conserved. For a uniform sphere, I=2/5MR² . Mass stays the sam... 1
- A solid sphere is rotating freely about its symmetry axis in free space. The radius of the sphere is increased keeping its mass same. Which of the following physical quantities would remain constant for the sphere ? Answer: 4. Angular momentum The sphere is in free space, so there is no external torque and angular momentum L=Iω is conserved. When the rad... 1
- Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities ω_1 and ω_2. They are brought into contact face to face coinciding the axis of rotation. The e… Answer: 1. 1/4 I(ω₁-ω₂)² Key idea: angular momentum is conserved when the discs join. Iω₁+Iω₂=2Iω⇒ω=ω₁+ω₂/2 . Loss =1/2Iω₁²+1/2Iω₂²-1/2(2I)ω... 1