To the potentiometer wire of L and `10Omega` resistance, a battery of emf 2.5 volts and a resistance R are connected in series. If a potential difference of 1 volt is balanced across L/2 length, the value of R is `Omega` will be

Options

A. 1
B. 1.5
C. 2
D. 2.5

Answer

C

Explanation

Just after collision
`v_(c ) = (10 xx 14 + 4 xx 0)/(10 + 4) = 10 m//s`
since spring force is internal force, it cannot change the linear momentum of the (two mass + spring) system. Therefore `v_(c )` remains the same.