Question 8
Parallel forces of 6 N and 4 N act on an object in the same direction. What force must be applied to make the resultant zero?
The right answer is the one marked above.
10 N in the opposite direction. The resultant of the original two is 6 N + 4 N = 10 N, so cancelling it takes that much force the other way.
2 N is 6 − 4 — but the original forces are not opposed, they act together. And 10 N in the same direction would raise the resultant to 20 N.