Question 3
When ploughing with a yoke of two bulls harnessed to a plough, one bull pulled with 100 N and the other with 80 N. With what resultant force is the plough drawn forward?
The right answer is the one marked above.
180 N. The bulls stand side by side so the pulls are parallel, but both are in the direction the plough has to go: 100 N + 80 N = 180 N.
20 N is the difference, which would apply only if the two bulls pulled against each other — and that would not be ploughing.