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