# A disc is freely rotating with an angular speed  on a smooth horizontal plane. If it is hooked at a rigid page  and rotates without bouncing about a point on its circumference. Its angular speed after the impact will be equal to a) b) c) d) None of these

## Question ID - 100220 | SaraNextGen Top Answer A disc is freely rotating with an angular speed  on a smooth horizontal plane. If it is hooked at a rigid page  and rotates without bouncing about a point on its circumference. Its angular speed after the impact will be equal to a) b) c) d) None of these

Answer Key / Explanation : (b) -

(b)

During the impact, the forces pass through point . Therefore, the torque produced by it about  is equal to zero

Consequently, the angular momentum of the disc about , just before and after the impact, remains the same

…(i)

Where   angular momentum of the disc about  just before the impact

angular momentum of the disc about  just after the impact

Just before the impact, the disc rotates about . But just after the impact, the disc rotates about