Chapter 5, Problem 4Q

At time t = 0, constant $\stackrel{\to }{F}$ begins to act on a rock moving through deep space in the +x direction. (a) For time t > 0, which are possible functions x(t) for the rock’s position: (1) x = 4t − 3, (2) x = −4t² + 6t − 3, (3) x = 4t² + 6t − 3? (b) For which function is $\stackrel{\to }{F}$ directed opposite the rock’s initial direction of motion?