ch05-p045

# ch05-p045 - 45. (a) The links are numbered from bottom to...

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45. (a) The links are numbered from bottom to top. The forces on the bottom link are the force of gravity mg G , downward, and the force G F 21 on of link 2, upward. Take the positive direction to be upward. Then Newton’s second law for this link is F 2on1 mg = ma . Thus, F 2on1 = m ( a + g ) = (0.100 kg) (2.50 m/s 2 + 9.80 m/s 2 ) = 1.23 N. (b) The forces on the second link are the force of gravity mg G , downward, the force G F 12 on of link 1, downward, and the force G F 32 on of link 3, upward. According to Newton’s third law 1on2 F G has the same magnitude as G F on . Newton’s second law for the second link is F 3on2 F 1on2 mg = ma , so F 3on2 = m ( a + g ) + F 1on2 = (0.100 kg) (2.50 m/s 2 + 9.80 m/s 2 ) + 1.23 N = 2.46 N. (c) Newton’s second for link 3 is F 4on3 F 2on3 mg = ma , so F 4on3 = m ( a + g ) + F 2on3 = (0.100 N) (2.50 m/s
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