A 3 Newton force and a 4 Newton force are acting concurrently on a point. Which force could not produce equilibrium with these two forces?

  1. 1N
  2. 7N
  3. 9N
  4. 4N

I'm confused. The book I'm looking at says that a 9 Newton force could not produce equilibrium with a 3 Newton and a 4 Newton force, but gives no clear explanation of why that is, could someone please explain? Thanks.

  • $\begingroup$ Research the triangle inequality. $\endgroup$
    – Bill N
    Jan 31, 2016 at 0:20
  • $\begingroup$ In addition to Bill's correct comment (which relies on the notion that vectors are forces) it might be worth explicitly constructing the cases cor the 1 and 7 Newton forces. The think about why neither 9 not 0.5 Newtons can do the trick. $\endgroup$ Jan 31, 2016 at 0:40

1 Answer 1


The max resultant force for these two forces would occur if they were both acting along the same line in the same direction. In that case they add algebraically. 3+4 = 7. Any other configuration of the forces gives an answer less than that.


Not the answer you're looking for? Browse other questions tagged or ask your own question.