## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

(a) If the box is at rest, then the tension is equal in magnitude to the weight. $T = mg$ $T = (50~kg)(9.80~m/s^2)$ $T = 490~N$ (b) If the box is moving at a steady speed, then the acceleration is zero. Then the tension must be equal in magnitude to the weight. $T = mg$ $T = (50~kg)(9.80~m/s^2)$ $T = 490~N$ (c) $\sum F = ma$ $T - mg = ma$ $T = m(a+g)$ $T = (50~kg)(5.0~m/s^2+9.8~m/s^2)$ $T = 740~N$ (d) $\sum F = ma$ $mg - T= ma$ $T = m(g-a)$ $T = (50~kg)(9.8~m/s^2-5.0~m/s^2)$ $T = 240~N$