Question # The vector sum of two force ( P ) and ( Q ) is minimum when the angle ( theta ) between their positive directions, is

# The vector sum of two force ( P ) and ( Q ) is minimum when the angle ( theta ) between their positive directions, is

(1) ( frac{pi}{4} )

(2) ( frac{pi}{3} )

(3) ( frac{pi}{2} )

(4) ( pi )

Solution

When ( theta=180^{circ} )

( begin{aligned} R ln 5 &=sqrt{A^{2}+B^{2}-2 A B} =& A(A-B)^{2}=A sim B end{aligned} )

[

begin{array}{rl}A geqslant R & R=R-B B>A & R=B-Aend{array}

]