** Newton vs Joule **

Joule and Newton are two units, which are widely used in the SI system. These units are extremely important, and a sound understanding in them is required. Read on to know, what Newton is, what Joule is, what are their definitions and finally the differences between Newton and Joule.

**What is Newton?**

To understand what a Newton is one must first understand the concept of force and linear momentum. The linear momentum of an object is equal to the mass of the object multiplied by the velocity of the object. Since the mass is a scalar and the velocity is a vector, the linear momentum is also a vector, which has the same direction as the velocity. According to Newton’s second law of motion, the net force acting on an object is proportional to the rate of change of linear momentum of that object. Therefore, net force =constant X momentum change / time. Force has the basic units kg m / s^{2}. To eliminate the proportionality constant, Newton is defined as the force required in changing the velocity of an object with a mass of 1 kilogram, by 1 meter per second, in 1 second. (i.e. accelerating an object with unit mass, by a unit velocity, on a unit time). The unit Newton is named after the eminent scientist Sir. Isaac Newton. It is used to measure force. The dimensions of force are [mass] [length] / [time] ^2.

**What is Joule?**

To understand what a Joule is, a proper understanding of the concepts energy and work are required. Energy is a non-intuitive concept. The term “energy” is derived from the Greek word “energeia”, which means operation or activity. In this sense, energy is the mechanism behind an activity. Energy is not a directly observable quantity. But it can be calculated by measuring external properties. Energy can be found in many forms. Kinetic energy, thermal energy and potential energy are to name a few. Energy can be given to a system in several ways. It can be given either by doing work on the system or directly as an energy transfer like heating the system. Imagine a solid mass of m kg on a frictionless flat, horizontal surface is given a net force F over a distance x. The initial kinetic energy of the system is zero and assuming the object takes a velocity v after the distance x the final kinetic energy is (mv^{2})/2. Since F = d(mv)/dt, by integrating both sides with respect to dx, the result F.x =(mv^{2})/2 can be obtained. It can be proven that the work done (i.e: the energy transferred) is F.x. Since the dot product is taken, the resultant energy is a scalar. The unit Joule is defined as the amount of energy transferred when a force of 1 Newton is applied on an object for a length of 1 meter. The basic unit of Joule is kg m^{2}/s^{2}. The dimensions of Joule are [mass][length]^{2}/[time]^{2}. The unit Joule is named in honor of the renowned scientist James Prescott Joule.

• Force, which is measured in Newton, is a vector while energy, which is measured in Joule, is a scalar. • Force is a method of transferring energy. |