The e.m.f. of a cell is 6 volt. When 2 ampere current is drawn from it then th e potential difference across its terminal remains 3 volt. Its internal resistance.

Explanation

Equation expressing momentum conservation is
`v_(A) + v_(B) = u_(A) + u_(B)` …(A)
Equation of coefficient of restitution is
`v_(B) - v_(A) = e u_(A) - e U_(B)m` …(B)
(a) From the above two equations, velocities `v_(A)` and `v_(B)` are
`v_(A) = ((1-e)/2)u_(A)+((1+e)/2)u_(B)` ...(i)
`v_(B) = ((1+e)/2)u_(A) + ((1-e)/2)u_(B)` ...(ii)
(b) For perfectly elastic impact `e = 1`, velocities `v_(A)` and `v_(B)` are
`v_(A) = u_(B)` ...(iii)
`v_(B) = u_(A)` ...(iv)
Identical bodies exchange their velocities after perfectly elastic impact.