How can we know that whether the quantity is vector or scalar? As we know that vector quantities have both magnitude & direction , & scalar only magnitude.

Question

waynex · Answer

Fundamentally, the definition of a quantity will contain this information. For instance, velocity is a vector. Speed, the magnitude of velocity, is a scalar.

anonymous · Answer

plus vector quantities are usually supported with a vector sign and with help of formula one can predict wether its a vector or not
E.G.: $$velocity = displacement \div time$$ 
since displacement is vector, so, velocity should also be a vector
hope that this helped

anonymous · Answer

check whether while measuring that quantity we need to specify the direction or not. for e.g.  when we say that this body has this much of mass then we cannot say that this mass is x in north direction or any other direction. I hope u could understand

jh3power · Answer

Vector: velocity, accelaration, force, displacement
Scalar: work, speed, distance
And, imagine that you are multiplying vectors by vectors. if it's cross product the answer becomes vector, and when it's dot product the answer is scalar. 
When you're multiplying scalars by scalars, it's a scalar. When you're multiplying vectors by scalars it's a vector.