Question

Suppose a friend is completing another physics assignment in their chair at their desk and you take the opportunity to turn this scenario into the physics question you now must complete. Your friend and chair have a combined constant moment of inertia of 5.2 kg m2, and the chair can freely rotate. Now your friend picks up two solid bricks (each of mass 1.2 kg) they accidentally collected from one of the campus buildings, and experiment with rotational kinematics. Supposing they hold the masses in each hand, arms outstretched, at distance of 0.7 m from their axis of rotation, and have an initial angular speed of 2.6 rev/s.

(a) Calculate the distance in m of each brick from your friend’s axis of rotation if they pull the bricks inward such that their rotational speed has increased to 3 rev/s.

(b) What is the initial rotational kinetic energy of the system?

(c) What is the final rotational kinetic energy of the system?

Answer 1

az Drital moment of thosha Iya To & amo2 = 5.2 + 2x 1.2 x (0.72 = 6.376 kam? Final moment of inertia If = To tam rp2 5.2 + 2x1.2 x rg 2 25.2 + 2.4582 ten momentum conservata. T, 7 - Тер 51 6:376 * 2.6 - (5.2 +2:47%) * 3 0.325866667 f = 0.36848 m = 0.37m Initial rotation at KE KE; at I w; 2 2 + 2 *6.376 * 2.6x269) ² 2850.7946404 P = 850.79 I a Final Ke kx (6-376 *2-6) (3x20 ) { 9 981-6861235 J ~981.693