In the diagram above, a rod 50 cm long of uniform cross-section is suspended horizontally on a fulcrum, F, by the action of two forces. What is the weight of the rod?
Attached Figure / Diagram
A
40N
B
80N
C
120N
D
200N
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Being a uniform rod, the height W should be acting at the mid point 25cm mark.
∴ Taking moment about the fulcrum, F,
200 x 10 = W x 10 + 40 x 30
2000 = 10W + 1200
=> 10W = 2000 - 1200
= 800
w = 800/10 = 80N
Source: Myschool Past Questions Archive (Record #14383)