Question

Can vector quantities be negative,positive and zero?

Answer 1

Yes vector quantities are positive and zero...
The negative sign of a vector quantity states that its direction is completely opposite to another reference vector which is taken as positive..
Hope it helps..

Answer 2

we can use '-' or '+' sign before Displacement which is a vector quantity and we can also use '-' or '+' sign before Joule which is a scalar quantity
With vectors, the sign determines the direction. If you change only the sign of a vector, you essentially have it point in the opposite direction. This is true for all kinds of vectors you encounter such as a force changing direction, velocity (moving in opposite direction,...