A particle of mass 1 gm and charge `1muC` is held at rest on a frictionaless horizontal surface at distance 1 m from the fixed charge 2mc. If the particleis released, it will be repelled . The spedd of the particle when it is at a distance of 10m from the fixed charge is

Options

A. `60ms^(-1)`
B. `100ms^(-1)`
C. `90ms^(-1)`
D. `180ms^(-1)`

Answer

D

Explanation

Change in kinetic energy = work done by electric field
`(1)/(2)mv^(2)-0=(V_(A)-V_(B))q=(Q)/(4piepsilon_(0))[(1)/(r_(1))-(1)/(r_(2))]xxq`
`(1)/(2)xx10^(-3)xxv^(2)=9xx10^(9)[1-(1)/(10)]xx10^(-6)xx2xx10^(-3)`
`v=180ms^(-1)`