Question

Point masses 1, 2, 3 and 4 kg are lying at the point (0, 0, 0), (2, 0, 0), (0, 3, 0) and (–2, –2, 0) respectively. The moment of inertia of this sytem about x-axis will be:

• A. 43 kg–m2
• B. 34 kg–m2
• C. 27 kg–m2
• D. 72 kg–m2.

Answer 1

Answer: (A)

43 kg–m2

Answer 2

$I _ { 1 } = I _ { 2 } = 0$ because these particles are placed on x-axis.

The M.I. of system about x-axis

= I1+I2+I3+I4=0+0+3×32+4×(–2)2=27+16=43 kg-m2.