Question

A disk and a sphere of same radius but different masses roll off on two inclined planes of the same altitude and length. Which one of the two objects gets to the bottom of the plane first ?

• A. Sphere
• B. Both reach at the same time
• C. Depends on their masses
• D. Disk

Answer 1

Answer: (A)

Sphere

Answer 2

$a = \frac{g \sin\theta}{1+ \frac{K^{2}}{R^{2}}}$
for disc ; $\frac{K^{2}}{R^{2}} = \frac{1}{2} = 0.5$
for sphere ; $\frac{K^{2}}{R^{2}} = \frac{2}{5} = 0.4$
a(sphere) > a(disc)
$\therefore$ sphere reaches first