Overview
This lecture reviews core physics concepts from motion to energy and thermodynamics, emphasizing essential formulas, definitions, and problem-solving techniques.
Motion & Graphs
- Uniform motion is movement at a constant speed in a straight line; shown as a straight line on a distance-time graph.
- Average speed equals distance divided by time; can also be found as the slope of a displacement-time graph.
- On speed-time graphs, a horizontal line indicates constant speed; a slanted line indicates acceleration.
- The area under a speed-time graph represents distance traveled.
Scalars vs. Vectors
- Scalar quantities have magnitude only (distance, speed, energy, time).
- Vector quantities have magnitude and direction (displacement, velocity, acceleration, force).
- North and East directions are considered positive; South and West are negative.
Velocity & Acceleration
- Velocity is the slope of a displacement-time graph or displacement divided by time.
- Acceleration is the change in velocity divided by time.
- On a position-time graph, a curve indicates acceleration; a straight line shows constant velocity.
Work & Energy
- Work is done when a force moves an object in the same direction as the force: Work = Force × Distance.
- Potential energy (gravitational): EP = mgh (mass × gravity × height).
- Kinetic energy: EK = ½mv² (½ × mass × velocity squared).
- To find mass or speed, rearrange the kinetic energy formula accordingly.
Conservation of Mechanical Energy
- Mechanical energy is the sum of kinetic and potential energies.
- In systems without energy loss, mechanical energy remains constant (EP_top = EK_bottom).
- For free fall: velocity = √(2gh).
Thermodynamics & Efficiency
- Systems can be open (exchange matter and energy), closed (only exchange energy), or isolated (exchange nothing).
- First law: Energy cannot be created or destroyed—only transformed.
- Second law: Heat naturally flows from hot to cold.
- Efficiency = (useful energy output / energy input) × 100%; cannot exceed 100%.
Energy Sources
- Renewable: solar, wind, water (if recycled), geothermal, tidal, biomass.
- Non-renewable: nuclear, fossil fuels.
Key Terms & Definitions
- Uniform Motion — constant speed in a straight line.
- Scalar Quantity — has only magnitude.
- Vector Quantity — has magnitude and direction.
- Velocity — displacement per unit time, direction matters.
- Acceleration — rate of change of velocity.
- Work — force applied over a distance.
- Potential Energy (EP) — stored energy due to position.
- Kinetic Energy (EK) — energy due to motion.
- Mechanical Energy — sum of potential and kinetic energy.
- Efficiency — percentage of useful energy output from total input.
Action Items / Next Steps
- Review significant digits and scientific notation.
- Practice solving problems with the provided formulas.
- Revisit definitions and differences between scalars and vectors.
- Study examples of energy conservation and efficiency calculations.