Energy Stores and Transfer
You'll encounter eight main energy stores in your physics studies: thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, and nuclear. Think of these as different "containers" where energy can be held - like money in different bank accounts.
Energy transfer happens in four main ways: mechanically (through forces), electrically (moving charges), by heating, and through radiation (light or sound). When any system changes, energy moves between these stores - it's never created or destroyed, just shifted around.
A closed system is like a sealed box where nothing gets in or out. The total energy always stays the same, which is why understanding energy transfer is so powerful for solving physics problems.
💡 Quick Tip: Remember that energy is conserved - if one store loses energy, another must gain it!
Kinetic Energy Store
Every moving object has energy in its kinetic store - from your walking pace to Formula 1 cars. The faster something moves or the heavier it is, the more kinetic energy it has.
Use the formula Ek = ½mv² to calculate kinetic energy. Notice how velocity is squared - this means doubling speed actually quadruples the kinetic energy! For example, a 3000kg car travelling at 20m/s has 600,000J of kinetic energy.
When objects slow down (like a braking car), energy transfers from the kinetic store to other stores, often heating up the surroundings through friction.
Gravitational Potential Energy Store
Lift anything off the ground and you're increasing its gravitational potential energy store. The higher and heavier the object, the more energy it stores - think of it as energy "waiting to happen."
The formula Ep = mgh shows how mass, gravitational field strength, and height determine this energy. When objects fall, energy transfers from gravitational potential to kinetic stores.
In reality, air resistance means some energy also transfers to thermal stores in the surroundings, which is why objects heat up slightly when falling through air.
Elastic Potential and Thermal Energy
Elastic potential energy builds up when you stretch or compress springs, elastic bands, or any bendable material. The formula Ep = ½ke² calculates this energy using the spring constant and extension.
Specific heat capacity measures how much energy different materials need to heat up. Using ΔE = mcΔθ, you can calculate energy changes when heating objects - essential for understanding everything from cooking to climate science.
Different substances need vastly different amounts of energy to change temperature by the same amount, which explains why water takes ages to boil but metal heats up quickly.