Question

Force `vecF` is acting on a particle having position vector `vecr`. Let `vectau` be the torque of this force about the origin. The correct equation is ______.

Options

• `vecr*vectaune0  "and"  vecF*vectau=0`

• `vecr*vectau=0  "and"  vecF*vectau=0`

• `vecr*vectaune0  "and"  vecF*vectaune0`

• `vecr*vectau=0  "and"  vecF*vectaune0`

Answer 1

Force `vecF` is acting on a particle having position vector `vecr`. Let `vectau` be the torque of this force about the origin. The correct equation is `underline(vecr*vectau=0  "and"  vecF*vectau=0)`.

Explanation:

Torque is given by `vectau=vecrxxvec"f"`

∴ `vectau` is perpendicular to `vecr` and `vecF`.

If two vectors are perpendicular, there dot product is zero.

`therefore vecr*vectau=0  "and"  vecF*vectau=0`