Chapter 5 - Work and Energy - Learning Path Questions and Exercises - Multiple Choice Questions - Page 172: 8

(b) kinetic energy decreases

Let a = angle between force and displacement Work = (Force)(d)cos(a) If 90 < a < 180, cos(a) < 0 Thus, when a > 90, Work < 0 Since Work = change in kinetic energy, negative work means kinetic energy decreases