MCQ
Figure shows two cases. In first case a spring (spring constant $K$ ) is pulled by two equal and opposite forces $F$ at both ends and in second case is pulled by a force $F$ at one end. Extensions $(x)$ in the springs will be
  • A
    In both cases $x=\frac{2 F}{K}$
  • In both cases $x=\frac{F}{K}$
  • C
    In first case $x=\frac{2 F}{K}$, in second case $x=\frac{F}{K}$
  • D
    In first case $x=\frac{F}{K}$, in second case $x=\frac{2 F}{K}$

Answer

Correct option: B.
In both cases $x=\frac{F}{K}$
b
(b)

Figure $(2)$ is $F.B.D.$ of figure $(1)$ at equilibrium $F=K x$

$x=F / K$

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