Answer to Question #144261 in Physics for Lennon

Question

A uniform horizontal beam, 6m long is supported at points A and B, 1m and 4m respectively, from one end, If the supporting force at B is 400N, calculate the mass of the beam and the supporting force at A.

Answer 1

For the equilibrium:

$$W=Mg=R_a+R_b$$

Taking moments about point A:

$$W(0.5(6)-1)=R_b(4-1)\\W=1.5(400)=600\ N$$

$$m=\frac{W}{g}=\frac{600}{9.8}=61\ kg$$

$$R_a=600-400=200\ N$$