We encourage you to interact with your colleagues here in conversations about this homework problem.

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Discussion and hints:

This problem is  a straight-forward application of the planar rigid body kinematics equations. Point O is fixed (zero velocity and zero acceleration), with the angular velocity and angular acceleration of the disk is given. To find the velocity and acceleration of point P on the L-shaped bar, you use the following:

v_P = omega x r_P/O
a_P = alpha x r_P/O – omega^2*r_P/O

Note that we use the geometry of the bar in writing down the position vector r_P/O for these equations; however, in the end, the shape of the bar has no bearing on the final answer. A straight bar between O and P produces the same result for the motion of P.

Using what we learned back in Chapter 1, can you identify times when the speed of P is increasing and when it is decreasing? (Hint: Look at the angle between the velocity and acceleration vectors.)

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