Answer to Question #178337 in Physics for Muhammad Abubakar Fayyaz

Question

TWO forces 5 N and 7 N are acting on a point. Which of the following cannot be their resultant force? 1 N, 3 N, 7 N, 8 N. 

Answer 1

Two forces can provide the maximal resultant force if and only if they are collinear and look in the same direction. In this case in order to obtain the resultant force we should add their magnitudes:

$$F_{max} = 5N + 7N = 12N$$

Two forces can provide the minimal resultant force if and only if they are collinear and look in the opposite direction. In this case in order to obtain the resultant force we should subtract their magnitudes (the smaller one from the bigger one):

$$F_{min} = 7N-5N = 2N$$

The magnitude of any other possible resultant force is then in this range: from $2N$ to $12N$. SInce $1N$ is out of this range, the answer is $1N$.

Answer. 1N.