Mechanical Engineering - Engineering Mechanics - Discussion

Discussion Forum : Engineering Mechanics - Section 5 (Q.No. 45)
45.
Two forces are acting at an angle of 120°. The bigger force is 40N and the resultant is perpendicular to the smaller one. The smaller force is
20 N
40 N
80 N
none of these
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
23 comments Page 3 of 3.

Onkar kadam said:   5 years ago
Just use Lami' Theorem,
F/sin30 = 40/sin90,
F = 20 N.
(5)

M.Chandra Sekhar said:   4 years ago
By Formula,


Tan90=40Sin120/(P+40Cos120)
Since Tan90 = Infinitive..
The term 'P+40Cos120' must be equal to 0.

Therefore,
P + 40Cos120 = 0.
P = -40(-1/2); [ Cos120=Cos(90+30) = -Sin30 = -1/2],
P = 20N.
(1)

M.Chandra Sekhar said:   4 years ago
By Formula,

Tan90=40Sin120/(P+40Cos120)
Since Tan90=Infinitive.
The term 'P+40Cos120' must be equal to 0.
Therefore,
P+40Cos120=0
P = -40(-1/2); [ Cos120=Cos(90+30) = -Sin30 = -1/2]
P = 20N.
(3)


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