A particle moves from point $\backslash ($ A $\backslash )$ to $\backslash ($ B $\backslash )$ under the action of a force $\backslash ($ F $\backslash ).$ When is the work done by $\backslash ($ F $\backslash )$ zero?

If $\backslash ($ F $\backslash )$ is perpendicular to the path $\backslash ($ A $\backslash$rightarrow B $\backslash )$ at each point

If $\backslash ($ F $\backslash )$ is a force due to friction $($hence along the path$)$

It can never be zero

If $\backslash ($ F $\backslash )$ is a conservative force