1.

A particle of charge `= 1 muC` and mass m=1 gm starts moving from origin at t = 0 under an electric field of `10^(3) N//C` along x-axis and magnetic field of 10 tesla along the same axis with the velocity of `vec(v) = 20 hat(j)` m/sec as shown, the speed of the particle at the time of `20 sqrt(3)sec` will be : A. 20 m/secB. 40 m/secC. 10 m/secD. None

Answer» Correct Answer - B
As `V^(2)=V_(x)^(2)V_(y)^(2)=((qE)/(m)t)^(2)+(20)^(2)`
`=((10^(-6)10^(3))/(10^(-3))20 sqrt(3))^(2)+(20)^(2)=1600`
`V = 40 m//sec`


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