A uniform wooden lath AB, 120 em long and weighing 1.20 N rests on two sharp-edged supports C and D placed 10 cmfrom each end of the lath respectively. A 0.20 N weight hangs from a loop of thread 30 em from A and a 0.90 N weight hangs similarly 40 em from B. Find the reactions at the supports.
Moments may be taken about any point, but, in this problem, the easiest equation ill be obtained if moments are taken about D. This will eliminate the moment due to the force (2.30 N – R) which acts through D
R x 100 = (0.20 x 80) + (1.20 x 50) + (0.90 x 30)
R x 100 = 16 + 60 + 27 = 103 N em units
R = 1.03 N
(2.30 N – R) = 1.27 N
Fig. 6.16. Forces on a supported lath
Answer. Reaction at C = 1.03 N Reaction at D = 1.27 N