MCQ
Two uniform solid spheres having unequal masses and unequal radii are released from rest from the same height on a rough incline. If the spheres roll without slipping:
  • A
    The heavier sphere reaches the bottom first.
  • B
    The bigger sphere reaches the bottom first.
  • C
    The two spheres reach the bottom together.
  • D
    The information given is not sufficient to tell which sphere will reach the bottom first.

Answer

  1. The two spheres reach the bottom together.

Explanation:

Acceleration of a sphere on the incline plane is given by:

$\text{a}=\frac{\text{g}\sin\theta}{1+\frac{\text{I}_{\text{COM}}}{\text{mr}^2}}$

ICOM for a solid sphere $=\frac{2}{5}\text{mr}^2$

So, $\text{a}=\frac{\text{g}\sin\theta}{1+\frac{2\text{mr}^2}{5\text{mr}^2}}=\frac{5}{7}\text{g}\sin\theta$

a is independent of mass and radii; therefore, the two spheres reach the bottom together.

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