A force `vecF=vecvxxvecA` is exerted on a particle in addition to the force of gravity, where `vecv` is the veocity of the particle and `vecA` is a constant vector in the horizontal direction. With what minimum speed a particle of mass m be projected so that it continues to move undeflected with a constant velocity?

Options

A. `(m)/(A)`
B. `(mg)/(A)`
C. `(A)/(mg)`
D. `(A)/(m)`

Answer

B

Explanation

Constant velocity, I,e net force =0
`|vec(v)xxvec(A)|=vAsintheta`
`vAsintheta=mg`
`v=(mg)/(Asintheta)`

v is minimim if `sintheta=1`
`v_(min)=(mg)/(A)`