Chapter 7, Problem 72P

In Fig. 7-49a, a 2.0 N force is applied to a 4.0 kg block at a downward angle θ as the block moves rightward through 1.0 m across a frictionless floor. Find an expression for the speed v_ƒ of the block at the end of that distance if the block’s initial velocity is(a) 0 and (b) 1.0 m/s to the right. (c) The situation in Fig. 7-49b is similar in that the block is initially moving at 1.0 m/s to the right, but now the 2.0 N force is directed downward to the left. Find an expression for the speed v_ƒ of the block at the end of the 1.0 m distance. (d) Graph all three expressions for v_f versus downward angle θ for θ = 0° to θ = 90°. Interpret the graphs.

Figure 7-49 Problem 72.