Joule and Newton are two units that are very useful in the SI unit system. These units are extremely important, and a sound understanding of them is necessary. The basic difference between Newton and Joule is their applications.
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/s2. To eliminate the proportionality constant, Newton is defined as the force required to change 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 unit time).
The unit Newton got its name after the eminent scientist Sir. Isaac Newton. We use it 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 of energy and work are necessary. Energy is a non-intuitive concept. The term “energy” comes 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 we can calculate it by measuring external properties. Energy can occur in many forms. Kinetic energy, thermal energy and potential energy are to name a few. Moreover, we can give energy to a system in several ways; either by doing work on the system or directly as an energy transfer like heating the system.
For instance, 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 (mv2)/2. Since F = d(mv)/dt, by integrating both sides with respect to dx, we can obtain the result F.x =(mv2)/2. Moreover, we can prove that the work done (i.e: the energy transferred) is F.x. Since we take the dot product, the resultant energy is a scalar.
We can define the unit Joule 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 m2/s2. The dimensions of Joule are [mass][length]2/[time]2. The unit Joule is named in honour of the renowned scientist James Prescott Joule.
What is the Difference Between Newton and Joule?
The force necessary to provide a mass of one kilogram with an acceleration of one meter per second is a Newton, and the joule is the amount of energy transferred when a force of 1 Newton is applied on an object for a length of 1 meter. The key difference between Newton and joule is that the unit Newton measures force while the unit joule measures energy. We denote Newton as N and joule as J. Moreover, Newton is a vector and joule is a scalar. This is another important difference between Newton and Joule.
Summary – Newton vs Joule
Newton and joule are important units in the SI unit system. The key difference between Newton and joule is that Newton is a unit that measures force, while Joule is a unit that measures energy.
1. “What Is a Newton.” com, Study.com, Available here.