Three forces act on an object. if the object is in translational equilibrium, which of the following must be true? i. the vector sum of the three forces must equal zero; ii. the magnitude of the three forces must be equal; iii. the three forces must be parallel.

Option I

Explanation:

When ever the system is in equilibrium, it means the net force on the system is zero.

If the number of forces acting on a system and then net force on the system is zero, it only shows that the vector sum of all the forces is zero.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.