NEET Physics Formula Sheet 2027

3.3 SCALARS AND VECTORS

Physical quantities fall into two broad classes. Some, like mass, time, temperature and energy, are fully described by stating a number and a unit; these are scalars, and they are added and subtracted by the ordinary rules of arithmetic. Others, such as displacement, velocity, acceleration and force, cannot be described properly unless a direction is also given; these are vectors. A vector has both magnitude and direction and combines with another vector according to the triangle law or the parallelogram law of addition.

Two vectors are equal only when their magnitudes are equal and they point in the same direction. Multiplying a vector by a positive number changes its length but not its direction, while multiplying it by a negative number also reverses its direction. A vector of zero magnitude is called the null or zero vector.

To add two vectors graphically, the second vector is drawn with its tail at the head of the first; the vector drawn from the tail of the first to the head of the second represents their sum, or resultant. The magnitude of the resultant of two vectors inclined at an angle θ is given by