1.

A particle having charge 'q' and mass 'm' is projected with velocity (4hati-6hatj+3hatk) m//sec from the origin in a region occupied by electric field 'E' and magnetic field 'B' such that vecB=B_(0)hati and vecE=E_(0)hatj (take (qE_(0))/m=2). Find the time (in sec) when the magnitude of velocity of the charge particle becomes 5sqrt(5) m//sec. (neglect the gravity)

Answer»


Solution :`v_(y)=u_(y)+a_(y)t`
`0=6-(qE_(0))/m t_(1)`
`t_(1)=3` sec
`v_(X)^(2)+v_(y)^(2)+v_(z)^(2)=(5sqrt(5))^(2)`
`4^(2)+v_(y)^(2)+3^(2)=125`
`v_(y)=10 m//sec`
`v_(y)=u_(y)+a_(y)t`
`10=0+(qE_(0))/m t_(2)`
`impliest_(2)=5` sec
So, `t=t_(1)+t_(2)=8` sec


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