iPad ? @100% · I Help IWH09 (Sections 10.1-10.5) Begin Date: 11/13/2017 3:30:00

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iPad ? @100% · I Help IWH09 (Sections 10.1-10.5) Begin Date: 11/13/2017 3:30:00 PMDue Date: 1/20/2017 3:30:00 PM End Date: 12/30/2017 6:00:00 AM (10%) Problem 9: Three identical point masses of mass M are fixed at the corners of an equilateral triangle of sides / as shown. Axis A runs through a point equidistant from all three masses, perpendicular to the plane of the triangle. Axis B runs through M, and is perpendicular to the plane of the triangle. Axes C, D, and E, lie in the plane of the triangle and are as shown. Axis A Axis Axis D Otheexpertta.com 20% Part (a) Determine an expression in terms of M and I for the moment of inertia of the masses about Axis A. Grade Summary Deductions 0% Potential 100% Attempts remaining:3 (4% per attempt) detailed view 45 6 Hint I give up! Hints: 4% deduction per hint. Hints remaining: Feedback: 5% deduction per feedback 20% Part (b) Determine an expression for the moment of inertia of the masses about Axis B in terms of M and /. 20% Part (c) Determine an expression for the moment of inertia of the masses about Axis C in terms of M and 1.

Explanation / Answer

a) moment of inertia about axis A is Ia = m*r1^2 + mr2^2 + mr3^2

r1 = r2 = r3 = L/sqrt(3)

then Ia = 3*m*r^2 = 3*m*(L/sqrt(3))^2 = 3*m*(L^2/3) = m*L^2

b) moment of inertia about axis b is Ib = m*r1^2 + mr2^2 + mr3^2

r1 = r2 = L*sqrt(3)/2

and r3 = 0

then Ib = 2*m*r^2 = 2*m*(L*sqrt(3)/2)^2 = (3/2)*m*L^2

C) moment of inertia about axis C is Ic = m*r1^2 + mr2^2 + mr3^2

r1 = r2 = L/2

and r3 = 0

then Ic = 2*m*r^2 = 2*m*(L/2)^2 = 2*m*(L^2/4) = m*L^2/2

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