Quantities which are having only magnitude but no direction are called scalar quantity.
Speed is the rate of change of displacement with respect to its surrounding. Since the speed of a body is irrespective of its direction, therefore it is a scalar quantity.
The rate of change of displacement of a body is called Velocity.
Velocity The rate of change of position of a particle in a given direction is called its velocity. Thus velocity is displacement made by the body per unit time. Velocity is a vector quantity.
Speed The rate of change of position of particle irrespective of direction is called speed. It is measured by distance covered per unit time. Speed is a scalar quantity.
Vector Quantities: Vector quantities refer to the physical quantities characterized by the presence of both magnitude as well as direction. For example, displacement, force, torque, momentum, acceleration, velocity, etc.
Linear displacement, Linear velocity and Linear acceleration all of these are vector quantities.
According to Newton's first law of motion every body continues in its state of rest or of uniform motion, in a straight line, unless it is acted upon by some external force.
The rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction in which the force acts. This statement is known as Newton's second law of motion