A projectile enters a resisting medium at x 0 with an initial velocity v0 900 ft/s and travels 4 in. before coming to rest.

A projectile enters a resisting medium at x  0 with an initial velocityv0  900 ft/s and travels 4 in. before coming to rest. Assuming that thevelocity of the projectile is defined by the relation 0 v  v  kx, where v isexpressed in ft/s and x is in feet, determine (a) the initial acceleration ofthe projectile, (b) the time required for the projectile to penetrate 3.9 in.into the resisting medium.