ball rotates around a shaft by two cords

1. The problem statement, all variables and given/known data
A 1.0kg ball is attached to a vertical rod by two strings. Each string is 1.0m long, and they are attached to the rod a distance of 1.0m apart. The rod-ball-strings setup is rotating about the axis of the rod. As it rotates the strings are taut and form an equilateral triangle. The tension in the upper string is 25N.
a. Describe a free-body diagram showing all the forces on the ball.
b. What is the tension in the lower string?
C WHat is the speed of the ball in rev/min?

I calculated tension in the lower string to be 8.2N, 36.9 degrees down and to the left. (I used arctan .3/.4 to caluclate the angle about the radius and used trig to solve tension) But should I have it as -8.2N as it is downward direction? Can tension be negative based on direction?

Part C:
I was using ∑F=ma-v^2/r and the sum of the forces on the X axis. Question again relates to direction – Should I have a negative value for the forceX of the second cord or are they added since they are both pulling in towards the shaft?


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