Page 147 - Schaum's Outline of Theory and Problems of Applied Physics

132 EQUILIBRIUM [CHAP. 11

Fig. 11-4

The tension in the rope provides the force applied to the crate. We note that the force on the crate exceeds the force ap-
pliedtotherope,whichiswhythis arrangementis usedinsteadof simplyapplyingthe 400-Nforceto the cratedirectly.

SOLVED PROBLEM 11.5

A boom hinged at the base of a vertical mast is used to lift a weight of 8000 N, as in Fig. 11-5(a). Find
the tension in the cable from the top of the mast to the top of the boom.
We begin by finding angles θ 1 and θ 2 . Since the sum of the interior angles of a triangle is always 180 ,
◦
◦
◦
◦
θ 1 = 180 − 40 − 65 = 75 ◦
Because the mast is vertical, it makes a 90 angle with the ground, and so
◦
◦
◦
θ 2 = 90 − 40 = 50 ◦

Fig. 11-5