Question

Can force be negative when

Answer 1

If the object being acted upon is stationary, the sum of all the forces is zero. So force A must be acting downwards, not upwards. A 'negative' force is one that is acting in the direction opposite to what you decide to be the positive direction (Usually, upward is +ve, downward is -ve).

Answer 2

Yes, force can be negative.
It means that the force is going to the opposite direction.

suppose, Question has an A and a B force pulling up and a C force pulling down. B is 2050N and C is 1450N. Figure out A. Isn't this a trick question?

Ans:- Trick question or teacher's typo. If the object being acted upon is stationary, the sum of all the forces is zero. 
A = -B + C = -2050N + 1450N = - 600N.

So force A must be acting downwards, not upwards. A 'negative' force is one that is acting in the direction opposite to what you decide to be the positive direction (Usually, upward is +ve, downward is -ve). 
If the object is accelerating, then the situation is different. A could be any value greater than -600N.

I hope this answer was helpful to you..........

Thank you