Mechanical Engineering - Engineering Mechanics - Discussion

Discussion Forum : Engineering Mechanics - Section 3 (Q.No. 42)
42.
The resultant of the two forces P and Q is R. If Q is doubled, the new resultant is perpendicular to P. Then
P = Q
Q = R
Q = 2R
none of these
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
12 comments Page 2 of 2.

JahnaNarayan Dhal said:   9 years ago
I can not understand how to find p + 2Qcos0 = 0. Please help me.

Popy said:   1 decade ago
Tan a= Qsin0/P+Qcos0.

When Q is double, then.

Tan90 = 2Qsin0/P+2Qcos0.

We know tan90 = infinity.

P+2Qcos0 = zero.

P = -2Qcos0.

R = root P^2+Q^2+2PQCOS0.

Putting P = -2Qcos0.

R = Q.


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