Answer to Question #178548 in Electrical Engineering for Hj Iuy

Question

1.Determine the reactions at A and B when (a) α = 0, (b) α = 90°, 

(c) α = 30°.

Answer 1

Consider a simple problem:

The force F is applied at the center of the rod. Hence, the reactions 1 and 2 at A and B will be equal.

(a) α = 0:

$$R_1+R_2+F=0,\\ 2R+F=0,\\\space\\ R=-\frac F2.$$

Reactions point to the right (opposite to the force)

(b) α = 90°, 

$$R_1+R_2+F\text{sin}90°=0,\\ 2R+F=0,\\\space\\ R=-\frac F2.$$

Reactions point opposite to F downward.

(c) α = 30°

$$R_1+R_2+F\text{sin}30°=0,\\ 2R+F\text{sin}30°=0,\\\space\\ R=-\frac{F\text{sin}30°}2.$$

Reactions point to the left bottom corner at the same angle below the horizontal.