Friction and air resistance are important forces that affect how energy works in physical systems. They are different from conservative forces, like gravity, because they don't store energy. Instead, they can cause energy to be lost as heat.

Friction

• What is it?: Friction is the resistance we feel when one surface or object slides over another.
• How it affects energy:
  • Friction changes kinetic energy (the energy of moving things) into thermal energy (heat). This means the total energy in a system goes down.
  • For example, if you slide an object across a rough surface, it can lose about 20% of its energy to friction after just a few meters.

Air Resistance

• What is it?: Air resistance is the force that pushes against an object as it moves through the air.
• How it affects energy:
  • The more quickly an object moves, the more air resistance it faces. We can get an idea of this force with a simple formula: $F_d = \frac{1}{2} C_d \rho A v^2$ In the formula:
  • $C_d$ = drag coefficient (a number that represents how smooth or rough the object is),
  • $\rho$ = air density (how thick the air is),
  • $A$ = area of the object facing the air,
  • $v$ = speed of the object.
• For example, when a car is going 100 km/h, air resistance can use up to 60% of its total energy.

Conclusion

Friction and air resistance are important when we talk about how energy is saved and used. They show how energy changes and can be wasted in real-life situations. Understanding these forces helps us find ways to use energy more efficiently.