Figure ( a ) shows a disk that can rotate about an axis at a radial distance h f

ID: 1288988 • Letter: F

Question

Figure (a) shows a disk that can rotate about an axis at a radial distance h from the center of the disk. Figure (b) gives the rotational inertia I of the disk about the axis as a function of that distance h, from the center out to the edge of the disk. The scale on the I axis is set by IA = 0.010 kgm2 and IB = 1.010 kgm2. What is the mass of the disk?
_______kg

Figure (a) shows a disk that can rotate about an axis at a radial distance h from the center of the disk. Figure (b) gives the rotational inertia I of the disk about the axis as a function of that distance h, from the center out to the edge of the disk. The scale on the I axis is set by IA = 0.010 kg½m2 and IB = 1.010 kg½m2. What is the mass of the disk?

Explanation / Answer

Calculate I at h = 0.1 m (or 0.2 m)

(IB - IA = 1)

Ih=0.1 = 0.01 + 2.5div (1kgm2 / 10div)

Ih=0.1 = 0.26 kgm2

Then apply

Parallel Axis Theorem with the following given

Then write two Parallel Axis Theorem Equations.

ICM = Ih=0 = 0.01 kgm2

ICM + md2

0.01 + md2

h = 0.1