Two horizontal forces act on a 6.3 kg chopping block that can slide over a frictionless kitchen counter, which lies in an xy plane. One force is F 1 = (6.8 N ) i+ (4.5 N ) j. Find the acceleration of the chopping block in unit-vector notation when the other force is (a) F 2 = (- 6.8 N) it (- 4.5 N) j, (b) F 2 = (- 6.8 N) i+ (4.5 N) j, and (c) F 2 = (6.8 N) i+ (- 4.5 N) j. (a) Number i + i i Units (b) Number i it i i Units (c) Number 1 it i i Units