# Spherical Polar co-ordinates

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

# Frame of reference and Rectangular Cartesian co-ordinate system

The motion of different bodies can be conveniently described if we imagine co-ordinate system attached to a rigid body and the positions of different bodies in space can be described w.r.t. it, then such co-ordinate system is called frame of reference.

# Center of mass : Dynamics of system of particles

## 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 2)

This article covers topics like Law of conservation of energy, Equation of motion and Form of motion under the effect of central forces.

## Law of conservation of energy

From equation 4 we consider

then this shows that is not only a central force but a conservative force. In this condition this equation

# Motion Under Central Forces (part 1)

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

## Introduction

If the force 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