A body of mass 1g and carrying a charge `10^(-8)`C passes from two points P and Q. P and Q are at electric potentials 600 V and 0 V respectively. The velocity of the body at Q is 20 `cms^(-1)`. It velocity in `ms^(-1)`at P is

Options

A. `sqrt(.028)`
B. `sqrt(.056)`
C. `sqrt(0.56)`
D. `sqrt(5.6)`

Answer

(a)

Explanation

According to law of conservation of energy ,
K.E = `1/2mv^(2) - 1/2 mu^(2)= qv = 1/2m[v^(2) - u^(2)] = qv`
`rArr u^(2)= v^(2) - 2qv^(2)/m = (0.2)^(2) - 2 xx 10^(-8) xx 600 / 10^(-3) = 0.028 `
`:. U = sqrt(0.028)`