1.

A solid sphere,a ring , and a disc all having same radius and same mass are made to roll on an inclined plane which one of them reaches fastest on ground

Answer»

Assume each object has the same mass and the same outside diameter.

ΣTA=IAα

I will assume clockwise ROTATION = positive,

∴mg(sinθ)R=(IA)α

but α=aR

∴mg(sinθ)R=(IA)aR

or

a=mg(sinθ)R2IA

but the PARALLEL axis theorm states IA=IC+mR2

a=mg(sinθ)R2IC+mR2

The object with the smallest mass moment of inertia (IC) will have the largest ACCELERATION down the plane.

Solid Sphere: IC=25mR2

Solid CYLINDER: IC=12mR2

Thin walled Hollow Sphere: IC=23mR2

The solid sphere wins the RACE



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