Lecture 2: Physics of Everyday Phenomena - Chapter 6

Introduction to Energy

• Chapter Overview: Introduction to energy concepts.
• Previous Lecture: Covered section 6.1, focusing on work and its relation to force. Work is a scalar and calculated as work = force x distance.

Energy and Work

• Energy Forms: Energy and work both have units of joules.
• Work: Calculated as force applied over a distance.
• Energy Conservation: Approach of using energy conservation to solve problems.

Kinetic Energy

• Definition: Energy associated with motion.
• Kinetic Energy Formula:
  • KE = 1/2 mv²
  • Objects at rest have zero kinetic energy.
• Work and Kinetic Energy:
  • Net work done on an object changes its kinetic energy.
  • Example: Pushing a crate increases its kinetic energy if net work is greater than zero.

Negative Work and Friction

• Negative Work: Work done by a force opposite to the direction of motion.
• Example: Car skidding to a stop due to friction.
  • Friction does negative work, reducing kinetic energy to zero.

Potential Energy

• Gravitational Potential Energy:
  • Defined as GPE = mgh.
  • Work done by lifting objects increases their gravitational potential energy.
• Elastic Potential Energy:
  • Stored in deformed objects like springs.
  • Formula: PE = 1/2 kx², where k is the spring constant.

Energy Conservation and Systems

• Conservative vs. Non-Conservative Forces:
  • Conservative forces (e.g., gravity, elastic) conserve mechanical energy.
  • Non-conservative forces (e.g., friction) convert mechanical energy to heat.
• Energy Tracking:
  • Conservation allows tracking energy between different forms.
  • Example calculations involve comparing initial and final energies, accounting for work done by forces like friction.

Springs and Hooke's Law

• Spring Behavior:
  • Linear relationship between force and displacement.
  • Defined by Hooke's Law: F = kx.
  • k is the spring constant, indicating stiffness.

Simple Harmonic Motion

• Definition: Motion that repeats in a sinusoidal pattern.
• Characteristics:
  • Involves cyclic processes like pendulums and springs.
  • Period (T) and frequency (f) describe the repetition rate.
  • Amplitude is the maximum displacement from equilibrium.

Key Concepts

• Mechanical Energy Conservation:
  • Total mechanical energy (potential + kinetic) is conserved in ideal systems.
  • Real-world applications involve accounting for losses (e.g., friction).

Conclusion

• Practicals: Examples of applying energy principles to solve physics problems.
• Applications: Concepts of energy are used to explain everyday phenomena and physical systems.