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In the diagram above, a rod 50 cm long of uniform cross-section is suspended hor...


Question

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?

Options

A) 40N

B) 80N

C) 120N

D) 200N


The correct answer is B.

Explanation:

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

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Dicussion (1)

  • 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

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