The vector sum of two forces is perpendicular to their vector differences. In that case, the forces
- are equal to each other
- are equal to each other in magnitude
- are not equal to each other in magnitude
- cannot be predicted.
Answer
(2) are equal to each other in magnitude
Solution
Let the forces be A and B.
∵ ( A + B) ( A - B) ⇒ ( A + B) ( A - B) = 0
⇒ A2 - A B + B A - B2 = 0
⇒ A2 = B2
∴ A = B: the forces are equal in magnitude (their directions may differ).
Answer: (2)