1.

A particle is moving with a constant acceleration `veca = hati-2hatj+2hatk m//s^(2)` and instantaneous velocity `vecv = hati+2hatj+2hatk m//s`, then rate of change of speed of particle 2 second after this instant will be :A. `(19)/(3)m//s^(2)`B. `3m//s^(2)`C. `(19)/(7)m//s^(2)`D. None of these

Answer» Correct Answer - C
A particle is …………
`vecv=(hati+2hatj+2hatk)+2(hati-2hatj+2hatk)`
`= hati +2hatj+2hatk+2hati-4hatj+4hatk`
`= 3hati-2hatj+6hatk`
`(d|vecv|)/(dt)=((3hati-2hatj+6hatk))/(sqrt(9+4+36))(hati-2hatj+2hatk)`
`= (19)/(7)`


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