Question

Two equal forces (P each )act at a point inclined to each other at angle of 120 degree.The magnitude of their resultant is :

a)P/2

b)P/4

c)P

d)2P

i only want the fastest method to solve this method because i have solved this already using resultant formula. any other faster methods?

Answer 1

Hmm, you want fastest method .
you can do it fast when you know some special result.
There are .....
1. When two equal vectors A are inclined 90° then, resultant = √2A
2. When angle between two equal vectors A is 120° , then resultant = A
3. When angle between two equal vectors A is 180° , then resultant = 0
4. When angle between two equal vectors A is 60° , then resultant = √3A

Now, come to the question,
Your question is " two equal force inclined 120° ,
So, resultant = P
Just 1 second is enough for answering.

Well you know method is Resultant = √{P² + P² + 2P.PCos120°} = P
So, option (C) is correct.

Answer 2

Answer:The ans. is P

Explanation:

=√ P^2 +P^2+2P^2×cos 120

=√2P^2+2P^2×(-1/2)

=√2P^2-P^2

=√P^2

= P