A car spark plug firing
The spark plug is the trigger that causes the gasoline to burn at a specific time in the car′s internal combustion engine, providing the gas/air mixture the activation energy to start to burn. This is a critical component in the thermodynamic cycle of an internal combustion engine. A dirty or poorly adjusted spark plug will cause an engine to mis-fire, or fail to run.
Matter and energy
When we discussed about motion, we had to describe the idea of motion in terms of displacement, velocity and acceleration. Then we asked, what causes motion? The answer was, "forces cause motion". Newton′s laws of motion give a framework for understanding motion in terms of inertia, force, momentum and impulse. Force is an unseen physical entity that is responsible for all motion. Force can be a contact force or an action at a distance force.
We can proceed with our inquisitiveness and ask next, what gives rise to force? The answer to this is that energy is responsible for force. And what is energy? Well energy is another of those mysterious physical entities that cannot be seen and is difficult to express. The concept most central to all of science and especially Physics, is energy. The combination of energy and matter makes up the whole universe. Matter is substance and energy is the mover of substance.
Matter is something that we can see, smell and feel. It has mass and occupies space. This is not so with energy. It is difficult to define energy, because it is not only an entity but also a process that gives rise to motion. Persons, places and substances have energy, but we usually observe energy only when it is happening – only when it is being transformed. It comes to us in the form of electromagnetic waves from the sun and we feel it as thermal energy (heat). Energy is captured by plants during photosynthesis, energy binds molecules of matter together and energy is in the food materials we eat. Even matter itself is condensed, bottled–up energy.
Energy is the thing that is all pervading and everywhere. It is an important concept of Physics. We will now discuss work and energy and how it is responsible for motion. We will also try to understand how rate of work (energy) or power, is responsible for many day to day applications.