Physics on the Move

• Speed is the rate at which an object covers distance. It is calculated as the distance traveled divided by the time taken. Speed is a scalar quantity and is typically measured in units like meters per second (m/s) or kilometers per hour (km/h).

• Acceleration is the rate of change of velocity of an object with respect to time. It is a vector quantity and can be calculated using the formula: acceleration = (final velocity - initial velocity) / time taken.

• Speed and acceleration are used in various real-world applications. Speed is crucial in transportation for calculating travel time, while acceleration is important in designing vehicles for efficient performance.

  • Examples include using speed limits for road safety and optimizing acceleration in sports cars for quick acceleration.

• Human Reaction Time: humans have a delay between their observation and acting which is around 0.25 seconds.

  • This can play a role when driving

  • The greater the speed of the vehicle, the greater the distance travelled during the same reaction time.

• Dangers involved with braking hard

  • Increased risk of skidding

  • Potential loss of control

  • Wear on tires and brakes

  • Rear-end collisions

  • Strain on suspension components

Energy On Earth

• Fossil Fuels

  • Derived from decomposed organic matter

  • Non-renewable due to long formation timescales

  • Combustion generates thermal energy for electricity

• Nuclear Fuels

  • Uranium and plutonium

  • Energy released through nuclear fission

  • Concerns about safety and waste disposal

• Biofuels

  • Derived from organic materials

  • Renewable and carbon-neutral

  • Used for electricity generation

• Wind

  • Kinetic energy of wind converted to electricity

  • Renewable and harnessed through turbines

• Hydroelectricity

  • Gravitational potential energy of water

  • Efficient and reliable

  • Electricity generated through turbines

• Trends in the use of Energy Resources

  • Energy consumption was very low before 1850.

  • Sharp rise in coal use in the late 1800s due to the industrial revolution.

  • Extraction of fossil fuels and crude oil increased from the early 1900s.

  • Nuclear power has risen since the late 1900s.

  • Renewable energy usage has increased recently, with hydroelectric and wind being prominent.

• The National Grid

  • Electrical power transferred at high voltages from power stations via overhead power lines.

  • Step-up transformers increase potential difference to reduce energy loss.

  • Step-down transformers decrease potential difference for domestic use.

• Domestic Electricity Supplies

  • Mains electricity is AC at 50Hz and 230V.

  • Direct electricity (DC) is constant and provided by batteries.

Beyond Earth

• Red shift is a phenomenon in which the light from an object moving away from an observer is shifted towards longer wavelengths, typically seen in astronomy as an indication of the expansion of the universe.
  

• Big Bang: The Big Bang theory is the prevailing cosmological model for the observable universe's earliest known periods. It suggests that the universe expanded from a high-density state, evolving into its current state over billions of years.

  • Evidence: Red Shift and CMBR

  • Cosmic Microwave Background Radiation (CMBR) is electromagnetic radiation filling the universe, a remnant from the Big Bang, detected in all directions.

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• Life Cycle of Star

  1. Dust and gas clouds present in a galaxy

  2. Gravitational attraction causes cloud to become denser

  3. Temperature and pressure increase

  4. Fusion of hydrogen to form helium, releasing energy

  5. Energy opposes gravity, forming a star

  6. Star runs out of gas, collapses

  7. Massive star collapses, produces supernova

  8. Supernova becomes neutron star or black hole

  9. Average star collapses, forms white dwarf
     
     

• Radiation emission is the process by which energy in the form of waves or particles is released from a source, such as radioactive materials or electromagnetic sources.

• Satellites are objects placed into orbit around the Earth or other celestial bodies to relay information, provide navigation, conduct research, or for other purposes.

  • They can be natural, like moons, or artificial, like communication or weather satellites.

  • Polar Orbit

    • Used for surveillance and weather forecasting

    • Orbits over poles at low height, ~90mins period

    • Covers entire earth quickly, good for scanning large areas

  • Geostationary Orbit

    • Used for communications

    • Orbits over equator, 24hrs period

    • Appears fixed from Earth, same angular speed

    • Allows fixed satellite dishes for uninterrupted data transfer

• Planetary Orbits

  • Gravitational force causes constant change in direction

  • Speed is constant, velocity changes

  • Closer orbit to sun increases gravitational attraction

  • Acceleration increases, orbital speed rises
    

• Temperature

  • Balance between absorbed and emitted radiation determines body temperature

  • Earth's temperature affected by greenhouse gases

  • Increase in greenhouse gases leads to global warming

• Earth’s Core

  • P waves pass through solids and liquids, S waves only through solids

  • Absence of S waves on opposite side of Earth suggests liquid core
    

• Deep Water

  • SONAR used to map ocean floor

  • Higher frequency waves reflect subtle differences, lower frequency waves penetrate deeper