Mass
Explanation
Physical quantities are broadly classified into two categories based on their directional properties: scalars and vectors. Scalar quantities are defined solely by their magnitude and do not have a specific direction. Vector quantities possess both magnitude and direction and must obey the laws of vector addition.
- Momentum: Momentum is defined as the product of mass and velocity ($\vec{p} = m\vec{v}$). Since velocity is a vector quantity, momentum is also a vector quantity, directed along the velocity of the object.
- Force: Force is an interaction that changes the motion of an object. It requires both magnitude (how strong the force is) and direction (where it is applied) to be fully described. Thus, it is a vector quantity.
- Velocity: Velocity is the rate of change of displacement with respect to time. Since displacement involves direction, velocity is inherently a vector quantity.
- Mass: Mass is a measure of the amount of matter contained in a body. It is described completely by its magnitude (e.g., 5 kg) and does not have any associated direction. Therefore, mass is a scalar quantity.
Key Takeaway: Mass is a fundamental scalar quantity possessing only magnitude, whereas momentum, force, and velocity are vector quantities that require both magnitude and direction for a complete description.