1. 18. (a) All forces are vertical and all distances are measured along an axis inclined at 30◦ . Thus, any
trigonometric factor cancels out and the application of torques about the contact point (referred to
in the problem) leads to
(15 kg) 9.8 m/s2 (35 cm) − (2.0 kg) 9.8 m/s2 (15 cm)
Ftripcep = = 1.9 × 103 N .
2.5 cm
(b) Equilibrium of forces (with upwards positive) leads to
Ftripcep + Fhumer + (15 kg) 9.8 m/s2 − (2.0 kg) 9.8 m/s2 = 0
and thus to Fhumer = −1.9 × 103 N, with the minus sign implying that it points downward.