Category Archives: Mechanics

Spherical Polar co-ordinates

This article is about Spherical Polar co-ordinates and is aimed for First year physics students and also for those appearing for exams like JAM/GATE etc.
The spherical polar coordinates represent the coordinates of points on the surface of a sphere in a co-variant form. The coordinates of the point P in this system is represented by the radial vector r which is the distance from the origin to the point, the polar or

Center of mass : Dynamics of system of particles

This article is about Center of mass and is for B.Sc. first year students of most of Indian universities. This topic comes under subject Mechanics taught in Ist year UG or B.Sc. classes.

What is center of mass?

Let us consider a body consisting of large number of particles whose mass is equal to the total mass of all the particles. When such a body is having translational motion then displacement is produced in each and every particle.
The center of mass of a body is defined as the point where whole mass of the system can be supposed to be concentrated.


External and internal forces (Dynamics of system of particles)

This lesson is about¬†External and internal forces (Dynamics of system of particles) . This chapter comes under subject Mechanics and is for B.Sc. Physics students.   While studying Newton’s laws of motion most of the time we have considered objects (for example planets, projectiles etc..) to be point particles rather then extended bodies. We did this because while dealing with problems like projectile motion or … Continue reading External and internal forces (Dynamics of system of particles) »

Motion Under Central Forces (part 1)

central forces notes

This article covers an introduction to central forces , equation of motion under central forces and


If the force \mathop f\limits^ \to acting on a body has following characteristics then it is a central force
(i) it depends on the distance between two particles
(ii) it is always directed towards or away from a fixed point.
Gravitational force is an example of central forces. Mathematically if we
consider central point as origin