REFER THE ATTACHED FIGURE. The shaft is massless. Two thin attached semi-circular discs of mass ‘m’=1kg is mounted on the shaft. Rotational speed of the shaft is ω=120 rad/sec. Neglect weight effect of attached masses. Bearings are at A and B. Take Z- axis along the shaft axis. X- axis is vertically downward. Y – axis is horizontal. Questions :- a> Look at the problem and tell whether it is a problem of pure static unbalance, pure dynamic unbalance, mixed unbalance. b> Use moment equation about ‘A’ and force equation to obtain the bearing reactions at ‘A’ and ‘B’. c> Replace the attached bodies by concentrated mass particles of mass equal to the bodies at their centre of masses. What will then be the bearing reactions. Look at the solution of part 2 and give your answer.
REFER THE ATTACHED FIGURE. The shaft is massless. Two thin attached semi-circular discs of mass ‘m’=1kg is mounted on the shaft. Rotational speed of the shaft is ω=120 rad/sec. Neglect weight effect of attached masses. Bearings are at A and B.
Take Z- axis along the shaft axis. X- axis is vertically downward. Y – axis is horizontal.
Questions :-
a> Look at the problem and tell whether it is a problem of pure static unbalance, pure dynamic unbalance, mixed unbalance.
b> Use moment equation about ‘A’ and force equation to obtain the bearing reactions at ‘A’ and ‘B’.
c> Replace the attached bodies by concentrated mass particles of mass equal to the bodies at their centre of masses. What will then be the bearing reactions. Look at the solution of part 2 and give your answer.
d> Put centrifugal forces in the model of part 3 and obtain bearing reactions using the equilibrium equation.
e> Rotate the shaft by 90 degrees and write the bearing reactions by observation of the previous result.
f> Under what practical condition is the neglect of weight of attached bodies justified.
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