Serway & Jewett — Angular Momentum: Problem 33

Review. A thin, uniform, rectangular signboard hangs vertically above the door of a shop. The sign is hinged to a stationary horizontal rod along its top edge. The mass of the sign is \( 2.40 \text{ kg} \), and its vertical dimension is \( 50.0 \text{ cm} \). The sign is swinging without friction, so it is a tempting target for children armed with snowballs. The maximum angular displacement of the sign is \( 25.0^\circ \) on both sides of the vertical. At a moment when the sign is vertical and moving to the left, a snowball of mass \( 400 \text{ g} \), traveling horizontally with a velocity of \( 160 \text{ cm/s} \) to the right, strikes perpendicularly at the lower edge of the sign and sticks there. (a) Calculate the angular speed of the sign immediately before the impact. (b) Calculate its angular speed immediately after the impact. (c) The spattered sign will swing up through what maximum angle?