Work is more than a way to make money and buy things, it’s also the energy we put in to achieving goals, changing the world for the better, and even forming relationships. We all have many different experiences with work — some of them good and some of them bad. Whether it be the discipline, wisdom, skill, or knowledge that we have gained through our work, or the time, passions, or relationships that we have lost due to our work – we are all changed by it.
The scientific definition of work involves transferring energy from one place to another, or changing its form. This is why it’s important to understand how to calculate the amount of work done, and that it requires a force to be exerted on an object, and there must be a displacement (or movement) of that object in the direction of that force.
A batsman hitting a ball, a boat sailing in the water, a cyclist pedaling a bike, a traveller pushing her luggage from the airport, or a cobbler polishing shoes are all examples of work. However, some things we think of as work in everyday circumstances are not actually work in the scientific sense, as they may involve a force but not a displacement, or a force but no movement, or even a combination of both.
When it comes to work, the direction of the displacement and the direction of the force are both important, as they determine whether the work is positive or negative. Work is a vector quantity, meaning it has both magnitude and direction, but because of the nature of scalar products in vector maths, it can only be given a value, and the SI unit for work is the joule.
The scalar product of a force F and the displacement d caused by that force is the work done, and it must have a direction to be positive or negative. However, if the force is constant and the displacement is constant, then work does not have a direction — it is simply a magnitude.
The following pictures show objects in motion, and you can click on the arrows to see if the work being done is positive or negative. One joule is equal to the energy expended (or work done) when a force of 1 newton causes an object to be moved a distance of one meter in its direction. The more force used, the greater the amount of work done. However, if the displacement is zero, then no work has been done at all.