a) The swing bar of mass m bar is pivoted as shown in the figure. Find the magni

Question

a) The swing bar of mass mbar is pivoted as shown in the figure. Find the magnitude of the angular acceleration (alpha) of the swing bar. Be sure to use the absolute value function in your answer, since no comparison of m1, m2, and mbar has been made.

Express your answer in terms of some or all of the quantities m1, m2, l, as well as the acceleration due to gravity, g. Enter the absolute value function as abs( ). For instance, enter abs (x*y) for |xy|.

b) In what direction will the seesaw rotate and what will the sign of the angular acceleration be?

a) The rotation is in the clockwise direction and the angular acceleration is positive

b) The rotation is in the clockwise direction and the angular acceleration is negative

c) The rotation is in the counterclockwise direction and the angular acceleration is positive

d) The rotation is in the counterclockwise direction and the angular acceleration is negative

Thank you! :-)

Explanation / Answer

a)The net torque acting about pivot =T= (m22l/3)+[mbar*(l/2 - l/3)]-m1l/3 = 2m2l/3 + mbarl/6 - m1l/3

moment of inertial of system about pivot point =I= m2*(2l/3)2+m1(l/3)2 + mbarl2/12 + mbar*(l/6)2 = 4m2l2/9 + m1l2/9 + mbarl2/12

Angular acceleration = T/I = (2m2l/3 + mbarl/6 - m1l/3)/( 4m2l2/9 + m1l2/9 + mbarl2/12)

b) Correct option is (b)

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