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
Discussion:
23 comments Page 1 of 3.
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.
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)
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.
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)
Onkar kadam said:
5 years ago
Just use Lami' Theorem,
F/sin30 = 40/sin90,
F = 20 N.
F/sin30 = 40/sin90,
F = 20 N.
(5)
Dibyendu Kundu said:
5 years ago
tan30°= Qsin120°/40+Qcos120°
0.577 = 0.866Q/40 + (-0.5Q),
23.08 - 0.28Q = 0.866Q,
23.08 = 0.866Q + 0.28Q,
23.08 = 1.146Q,
Q = 20.139 (approx 20N).
0.577 = 0.866Q/40 + (-0.5Q),
23.08 - 0.28Q = 0.866Q,
23.08 = 0.866Q + 0.28Q,
23.08 = 1.146Q,
Q = 20.139 (approx 20N).
Rushi jadhav said:
5 years ago
40cos(120)
Cos(120) =-0.5=-1/2.
40*(-1/2) =-20.
-20 shows that it is in opposite directions.
Cos(120) =-0.5=-1/2.
40*(-1/2) =-20.
-20 shows that it is in opposite directions.
Arifkhan said:
5 years ago
Cos@=bas/hyp.
Cos120=smaller-force /40,
And we get;
Smaller force = 20.
Cos120=smaller-force /40,
And we get;
Smaller force = 20.
Rajdeep Singh said:
5 years ago
(120°-90°)=30°.
40sin(30°)=40*1/2=20N(force in opposite direction to smaller force).
Hence forec in smaller direction is - 20N.
Hence option D is the correct answer to this question.
40sin(30°)=40*1/2=20N(force in opposite direction to smaller force).
Hence forec in smaller direction is - 20N.
Hence option D is the correct answer to this question.
Gurunathan said:
6 years ago
tan@=1/0=Qsin 120/Q+40 cos 120.
By cross multiplying we get;
Q-20=0.
So Q= 20.
By cross multiplying we get;
Q-20=0.
So Q= 20.
Khanka said:
6 years ago
If one angle is 120 then the other two must be less than 90.
Prashant said:
6 years ago
Simply take the components of force Q in x and Y direction.
Y direction gives magnitude of resultant and,
X direction gives magnitude of force P in opposite direction.
i.e. P - Qcosθ=0.
P = Q cosθ.
P = 40 cos60.
P = 20 N.
Y direction gives magnitude of resultant and,
X direction gives magnitude of force P in opposite direction.
i.e. P - Qcosθ=0.
P = Q cosθ.
P = 40 cos60.
P = 20 N.
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