Mechanical Engineering - Engineering Mechanics - Discussion

Discussion Forum : Engineering Mechanics - Section 1 (Q.No. 10)
10.
If the resultant of two equal forces has the same magnitude as either of the forces, then the angle between the two forces is
30°
60°
90°
120°
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
35 comments Page 2 of 4.

Krishna said:   1 decade ago
cos(120) = cos(90+30) = -sin30 = -0.5.

Murali Raj K said:   10 years ago
Both the forces are equal thus the resultant is also equal.

Total angle is 360.

Three forces are acting equally thus 360/3=120.

Abdul Khaleque said:   10 years ago
p2 = p2+p2+2p.pcosθ.
p2 = 2p2+2p2cosθ.

-p2 = 2p2cosθ.
cosθ = -1/2.
θ = 120.

Tushar Chakraborty said:   10 years ago
Law of Cosine- R^2=P^2+Q^2-2PQ Cosθ

So θ = 60°

When Forces are Nose to tail, θ = 60°

When Forces are Tail to Tail, θ = 180°-60° = 120°

Shams said:   10 years ago
The angle is 60 and not 120. It can be clearly understood from equilateral triangle and total angle in a triangle. And also from the cosine rule: A^2 = B^2+C^2-2BC cosA.

Musliu said:   10 years ago
The correct answer is 120 bc the magnitude re the same.

So therefore R = P the Law of cosine R^2 = R^2 +R^2 - 2R*R (Cosθ).

R^2 - 2 R^2 = - 2R^2COSθ.

- R^2/R^2 = - 2COSθ.

1/2 = COSθ.

Cos^-10.5 = y.

y = 120.

Hamed said:   9 years ago
2 x p x cos 120 = R.
p = R.

Ankit ughade said:   9 years ago
For getting the equilibrium condition all these forces must have the same angle to each other.

Hence 360/3 = 120.

P.Chilambarasan said:   9 years ago
R^2 = P^2 + q^2 + 2pq Cosθ.
R = P = Q = F.

Substitute F in the equation, you get Cosθ = -1.
So, θ = 180°.

Dhanendra said:   9 years ago
Correct answer will be 60θ as in fcosθ plus fcosθ equal to f which gives θ equal to 60θ.


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