Question

A ring solid sphere and a disc are rolling down from the top of the same height, then the sequence to reach on surface is

• A. Ring, disc, sphere
• B. Sphere, disc, ring
• C. Disc, ring, sphere
• D. Sphere, ring, disc

Answer 1

Answer: (B)

Sphere, disc, ring

Answer 2

Time of descent $\propto$ moment of inertia $\propto \frac{k^{2}}{R^{2}}$

$\left( \frac{k^{2}}{R^{2}} \right)_{sphere} = 0.4$, $\left( \frac{k^{2}}{R^{2}} \right)_{disc} = 0.5$, $\left( \frac{k^{2}}{R^{2}} \right)_{ring} = 1$

∴ $t_{sphere} < t_{disc} < t_{ring}$.