1.) A uniform rod of mass 0.93 kg is 17 m long. The rod is pivoted about a horizontal, fric- tionless pin at the end of a thin extension (of negligible mass) a distance 17 m from the cen- ter of mass of the rod. Initially the rod makes an angle of 70 degrees with the horizontal. The rod is released from rest at an angle of 70 degrees with the horizontal. The acceleration of gravity is 9.8 m/s^2. Hint: The moment of inertia of the rod about its center-of-mass is 1/12 ML^2. What is the angular speed of the rod at the instant the rod is in a horizontal position? Answer in units of rad/s. MgL/2 = .5(1/12ML^2)w^2 This works out to be: w = sqrt(12g/L) w = 2.630142 ??? But the answer is wrong?!?! why?! --------------------------------------- 2. Two pulley wheels, or respective radii R1 = 0.34 m and R2 = 1.5 m are mounted rigidly on a common axle and clamped together. The combined moment of inertia of the two wheels is I + 4.5 kg*m^2. Mass m1 = 18 kg is attached to a cord wrapped around the first wheel, and another mass m2 = 5.9 kg is attached to another cord wrapped around the second wheel. The acceleration of gravity is 9.8 m/s^2 : Find the angular acceleration of the system. Take clockwise direction as positive. Answer in units of rad/s^2. I = .5MR^2 I1= .5(18)(.34)^2 I2= .5(5.9)(1.5)^2 I = I1 +I2 + 4.5 = 12.1779 Acceleration= [(m2gR2)-(m1gR1)]/[I+(m1r1^2)+(m2r2^2)] = .971689752 ?!?! This is wrong as well, WHY!?!?!? Please help. All help is appreciated.