UPSC Civil Service Exam Questions - Engineering

Q1:

A horizontal rod AB carries three loads of 3.0 kg, 7.0 kg and 10.0 kg at distances of 2.0 cm, 9.0 cm and 15 cm respectively from A where it is hinged. Neglecting the weight of the rod, which is the point at which the rod will be balance ?

A 10.95 cm form A

B 11.25 cm from A

C 12.55 cm from A

D 13.25 cm form A

ANS:A - 10.95 cm form A

RESULTANT* FORCE DISTANCE OF RESULTANT ACT FROM SUPPORT = SUM OF MOMENT
R * x = M.
R = 3+7+10 = 20 KG.

SUM OF M ABOUT B = (3*2)+(7*9)+(10*15) =219 KG.cm.
219= 20x,
x = 219/20 = 10.95cm.