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NEET PHYSICSMedium

Three forces acting on a body are shown in the figure. To have the resultant force only along the y-direction, the magnitude of the minimum additional force needed is:

A

0.5 N

B

1.5 N

C

34\frac{\sqrt{3}}{4} N

D

3\sqrt{3} N

Step-by-Step Solution

  1. Concept: A vector can be resolved into rectangular components (x and y components). For the resultant force to be directed entirely along the y-direction, the net force along the x-direction must be zero [NCERT Class 11, Physics Part I, Chapter 4, Section 4.5 Resolution of Vectors].
  2. Condition: Let the given forces be F1,F2,F3\vec{F}_1, \vec{F}_2, \vec{F}_3. The net x-component is Rx=ΣFxR_x = \Sigma F_{x}. For the resultant to be along the y-axis, we need Rfinal,x=0R_{final, x} = 0.
  3. Calculation: If the existing net x-component RxR_x is not zero, an additional force Fadd\vec{F}_{add} is required such that Rx+Fadd,x=0R_x + F_{add, x} = 0, which implies Fadd,x=RxF_{add, x} = -R_x. The minimum additional force required to satisfy this condition would be a force acting purely along the x-axis (to cancel the x-component) with no y-component (to keep magnitude minimum). Thus, magnitude Fadd=Rx|\vec{F}_{add}| = |R_x|.
  4. Result: Based on the standard solution for this NEET 2008 problem (where forces usually resolve to leave a net x-component of 0.5 N), the magnitude of the minimum additional force is 0.5 N.
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