If `vec F` is the force acting in a particle having position vector `vec r` and `vec tau` be the torque of this force about the origin, then

Options

A. `vec(r).vec(tau)=0"and"vec(F).vec(tau)=0`
B. `vec(r).vec(tau)=0"and"vec(F).vec(tau) ne 0`
C. `vec(r).vec(tau) ne 0"and"vec(F).vec(tau) = 0`
D. `vec(r).vec(tau) ne 0"and"vec(F).vec(tau) ne 0`

Answer

A

Explanation

`vec(tau)=vec(r)xxvec(F)`
`vec(tau)_|_ vec(r)"and"vec(tau)_|_vec(F) i.e. vec(tau),vec(r)=0"and"vec(tau).vec(F)=0`