Question

A uniform disk of radius 0.529 m and unknown mass is constrained to rotate about a perpendicular axis through its center...


A uniform disk of radius 0.529 m and unknown mass is constrained to rotate about a perpendicular axis through its center. A ring with the same mass as the disk is attached around the disk's rim. A tangential force of 0.237 N applied at the rim causes an angular of 0.119 rads/s^2. Find the mass of the disk

Answer

Radius of the disk (R)=0.529 m

Tangential force applied on the rim (F)=0.237 N

Angular acceleration of the disk and ring system (α)=0.119 rad/s2

Since the ring is attached to the rim of the disk, the radius of ring will be equal to the radius of the disk.

Therefore, we can find the moment of inertia of this system using the equation;

RF=Iα

Therefore;

I=RFα

Substituting the values;

I=0.529×0.2370.119

I=1.053 kg m2

The moment of inertia of the disk and ring system is given by;

I=12MR2+MR2=32MR2

Hence, we can write for the mass of the disk and the rim as;

M=2I3R2

Substituting the values;

M=2×1.0533×(0.529)2

M=2.51 kg

Therefore, the mass of the disk is 2.51 kg.

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