申論題

6.(20%) A projectile enters a resisting medium at x = 0 with an initial velocity vo = 270 m/s and travels 100 mm before coming to rest. Assuming that the velocity of the projectile is defined by the relation v = vo - kx, where v is expressed in m/s and x is in m, determine (a) the initial acceleration of the projectile. (b) the time required for the projectile to penetrate 97.5 mm into the resisting medium.