Can a reaction have zero activation energy ?

Can a vector be zero if any of its components is not zero?

Can any of the components of a given vector have greater magnitude than that of the vector itself ?

Answer the following : (i) A vector has magnitude & direction. Does it have a fixed location in space? Can it vary with time. (ii) Will two equal vectors vec(a) & vec(b) at different locations in space necessarily have identical physical effects? (iii) Can three non zero vectors, not in one plane, give a zero resulatnt? Can four vectors do ? (iv) Can a vector have zero magnitude if one of its components is not zero?

Can a body have zero velocity and finite acceleration?

A body can have constant speed and still have varying velocity.

Can a body have zero velocity and still be accelerating ? If yes gives any situation.

Can any object have momentum even if its mechanical energy is zero?

Can a reaction have negative or zero activation energy ?