3. Only two forces act on an object. The magnitude of the first force is 25 N and it acts at an angle of +25° with the positive x-axis. The second force acts at angle of -73° with the positive x-axis. The acceleration of the object is parallel to the positive x-axis. What is the magnitude of the second force?

Fr = 25N.[25o] + F2[-73o]

Since the acceleration is parallel to
the x-axis, the sum of Y components of velocity equals 0:

25*sin25 + F2*sin(-73) = 0.
10.57 -0.956F2 = 0.
-0.956F2 = -10.57.
F2 = 11.1N[-73o].