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If a body contains no planes of symmetry, the principal moments of inertia can be determined mathematically. To show how this is done, consider the rigid body which is spinning with an angular velocity ω, directed along one of its principal axes of inertia. If the principal moment of inertia about this axis is I, the angular momentum can be expressed as H = Iω = Iωx i + Iωy j + Iωz k. The components of H may also be expressed by Eqs. 21–10, where the inertia tensor is assumed to be known. Equate the i, j, and k components of both expressions for H and consider ωx, ωy, and ωz to be unknown. The solution of these three equations is obtained provided the determinant of the coefficients is zero. Show that this determinant, when expanded, yields the cubic equation
I3 – (Ixx + Iyy + Izz)I2
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Engineering Mechanics: Dynamics (14th Edition)
- The assembly in figure 1 is rotating counterclockwise from above at w = 10 rad/s about the z axis. The thin disk has mass 12 kg and radius 15 cm, while, and the thin rod CD has mass 3 kg and length 30 cm. axis. @=10 rad/s B C A 15 cm Figure 1 30 cm Find the inertia tensor for the disk and rod CD about the axis CD. Calculate the moment of inertia of the disk and rod CD about the vertical z Determine the angular momentum of the disk and rod CD about the z axis.arrow_forwardGiven that P = 50N, and the rod has mass = 0.370 kg with centroidal mass moment of inertia l = 37/19200 kg-m²:a. Which of the equations given in the second image can be used to solve for the angular acceleration of rod BD?b. What is the angular acceleration of rod BD?arrow_forwardM M 1.5m m M m = 2kg. M = 3.5kg a) justify whether the moment of inertia about the vertical or horizontal axis have smaller value. Show your calculation. (b) Given angular velocity of 80 rev s¹ in 240 rev. Has a moment of inertia of 1.41x10-3 kg m2. Find: (i) angular acceleration. (ii) net constant torque must apply (c) A space station consists of a giant rotating hollow cylinder of mass 10 kg including people on the station and a radius of 100 m. Given initial angular velocity of 3.3rpm in order to generate artificial gravity. If 100. people, each with an average mass of 65 kg spacewalk to an awaiting spaceship. Find the new angular velocity (in rpm) once all the people are off the station. (d) Suppose a child walks from the outer edge of a rotating merry-go-round to the center. What happend to the angular velocity of the merry-go-round does it increase, decrease, or remain the same? By using the conservation of angular momentum, explain your answer qualitatively.. A large train has…arrow_forward
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