Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Since the surface is frictionless, the only possible horizontal force is the force from the tension in the rope. (a) Since the box is at rest, $T = 0$ (b) Since the box is moving at a steady speed, the acceleration is zero. Therefore, $T = 0$ (c) We can use a force equation to find $T$ $T = ma_x$ $T = (50~kg)(5.0~m/s^2)$ $T = 250~N$