Work and Power Lecture Summary

Work

• Definition: Paglipat ng enerhiya mula sa isang pisikal na sistema patungo sa iba.
  • Formula:
    • $W = Fs$
    • $W = Fs \cos \theta$
  • Unit: Joules, ergs, foot-pounds
• Examples:
  • Pagtulak ng isang object o pagbuhat ng isang balde.
• Formulas:
  • Direct (horizontal) force: $W = Fs$
  • Inclined force: $W = Fs \cos \theta$

Force and Formulas

• Force can vary based on different physics topics:
  • Newton's Law: $F = ma$
  • Circular motion: $F = \frac{mv^2}{R}$

Energy Units and Conversion

• SI MKS: Newton-meter = Joules
• SI CGS: Dines-centimeter = Ergs
• British Units: Pound-feet
• Conversions:
  • 1 Joule = 1 Newton-meter
  • 1 Joule = 0.7376 lb-ft
  • 1 lb-ft = 1.356 Joules

Problem Solving

• Example problem involving work done by multiple forces and friction.
• Total work calculated by summing individual works and considering opposing frictional force.

Power

• Definition: Bilis ng paggawa ng trabaho.
  • Formula:
    • $P = Fv$
    • $P = \frac{W}{t}$
    • $P = \frac{mgh}{t}$
• Units: Watts, horsepower (HP)
• Conversions:
  • 1 HP = 550 ft-lb/s = 746 watts
  • 1 kWh = 3.6 x $10^6$ Joules

Solving Power Problems

• Calculate power based on given force and velocity, or weight and height over time.
• Examples demonstrating both methods.

Energy

• Definition: Work done by a system.
  • Focus on kinetic and potential energies.
• Kinetic Energy: Energy in motion.
  • Formula: $K = \frac{1}{2}mv^2$
  • Unit: Joules (SI MKS), Ergs (SI CGS), lb-ft (British)

Potential Energy

• Definition: Energy at rest.
  • Dependent on height.
  • Formula: $U = mgh$

Conservation of Energy

• Energy can be converted but not created or destroyed.
• Law of Conservation of Energy:
  • Formula: $\Delta K + \Delta U + \Delta U_{int} = 0$
• Examples showing energy conversion from potential to kinetic.

Problem Solving

• Use conservation of energy to solve problems, calculating velocity or energy based on initial conditions.

Important Concepts and Formulas

• Work and its dependence on force and motion direction.
• Power as a time-dependent measure of work.
• Energy conservation and conversion between kinetic and potential forms.

Conclusion

• Remember the key formulas and concepts.
• Practical applications through problem-solving examples.

End of notes.