Question

For the beam shown in Figure calculate (a) the force acting on support A, (b) distance d, neglecting any forces arising from the mass of the beam.

Answer 1

(a) (The forces acting in an upward direction) = (the forces acting in a downward direction)

Hence (RA + 40) N = (10 + 15 + 30) N

R_A = 10 + 15 + 30 − 40

= 15 N

(b) Taking moments about the left-hand end of the beam and applying the principle of moments gives:

clockwise moments = anticlockwise moments 

(10 × 0.5) + (15 × 2.0) N m + 30 N × d

= (15 × 1.0) + (40 × 2.5) N m

i.e. 35 N m + 30 N × d = 115 N m from which, distance,

d =(115 − 35) N m/30 N = = 2.67 m