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Wright State University Department of Mechanical and Materials Engineering Spring 2011 ME 213 DYNAMICS: MIDTERM EXAM 2 Open Book, Closed Notes, DO NOT Write on this Sheet Show All Work for Partial Credit Problem 1 (20 points): The 20-kg block A slides along the smooth slot. Spring B has a spring constant of 1000 N/m, and spring C has a spring constant of 500 N/m. In the position shown, spring B is stretched 0.8 m, spring C is unstressed, and the block has a velocity of 10 m/s down the slot. Using the conservation of energy principle, determine the velocity of block A when it reaches position D. Problem 2 (20 points): The 4-oz baseball is thrown horizontally toward a batter at 60 ft/s. After being struck by the bat A, the velocity of the ball is 120 ft/s in the direction shown. Determine the magnitude and direction of the average force applied to the ball by the bat during the 0.02-s contact period. Problem 3 (15 points): A 0.08-lb bullet is fired from a rifle that is clamped to a trolley. The combined weight of the rifle and trolley is 20 lb. After firing, the velocity of the trolley is known to be vA = 4.8 ft/s to the left. Calculate vB, the velocity of the bullet after firing, and the muzzle velocity (the velocity of the bullet relative to the barrel of the rifle). Problem 4 (45 points): A system consists of three particles that have the velocities shown at a certain instant. Compute the following for the system: (a) the coordinates of the mass center G; (b) the linear momentum; and (c) the angular momentum about the origin. B C A