A force is a push or pull factor. Net force is the sum of all forces acting upon an object. For instance, if the thrust of a car on a horizontal surface was equal to 1000N1000N forwards, and the drag was equal to 800N800N backwards, the net force would be
1000 +(-800)1000+(−800)
=1000-800=1000−800
=200N=200N forwards.
However, if the thrust was equal to 800N800N forward, and the drag was equal to 1000N1000N backward, the net force would be
800+(-1000)800+(−1000)
=800-1000=800−1000
=-200=−200
=200N=200N backwards. We don't say -200N−200N backwards, because that is the same as saying 200N200N forwards. We could say -200N−200N forwards, because that is the same as 200N200N backwards, but in this example I have chosen not to.
In the question, there are two forces acting upon an object. One is John's force of 10N10N, and the other is Daniel's opposite force of 12N12N. Add them together and you get
10+(-12)10+(−12)
=10-12=10−12
=-2=−2
=2N=2N in Daniel's direction (remembering this is the same as -2N−2N in John's direction).
I hope I helped!
