# Chapter 6 - Dynamics I: Motion Along a Line - Exercises and Problems - Page 161: 11

(a) T = 490 N (b) T = 490 N (c) T = 740 N (d) T = 240 N

#### Work Step by Step

(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) $\sum F = ma$ $mg - T= ma$ $T = m(g-a)$ $T = (50~kg)(9.8~m/s^2-5.0~m/s^2)$ $T = 240~N$

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