physics(syllabus)

• Fundamental quantities cannot be expressed as another quantity e.g. length, time
• Derived quantities are combinations of fundamental quantities e.g. speed is distance per unit time
• Five base quantities at this level are:

  • Length (unit: meters)
  • Mass (unit: kilograms)
  • Time (unit: seconds)
  • Current (unit: amperes)
  • Temperature (unit: kelvin)
• Other base quantities are:

  • Amount of substance (unit: moles)
  • Luminous intensity (unit: candelas)
• Derived quantities include:

  • Area (unit: meter squared or meter by meter)
  • Volume (unit: meter cubed or meter by meter by meter)
  • Pressure (unit: pascals or newton per meter squared)
  • Force (unit: newtons or kilogram meter per second squared)
  • Charge (unit: coulomb, which is an ampere second)
• Prefixes to know at CXE level:

  • Micro (10^-6, divide by a million)
  • Milli (10^-3, divide by a thousand)
  • Centi (10^-2, divide by a hundred)
  • Kilo (10^3, multiply by a thousand)
  • Mega (10^6, multiply by a million)
• Examples of unit conversion:

  • 5600 milliseconds to seconds: 5600 / 1000 = 5.6 seconds
  • 300 centimeters to meters: 300 / 100 = 3 meters
  • 2.5 kilowatts to watts: 2.5 * 1000 = 2500 watts
• Scalars have magnitude but no direction e.g. distance, speed

  Vectors have magnitude and direction e.g. displacement, velocity
• Forces enable masses to overcome inertia and cause changes in motion, shape, and size
• Forces are measured in newtons (kg m/s^2)

  • Forces include: tension, normal, friction, weight, air resistance
• In equilibrium, net force is zero, no change in motion

  • Objects accelerate at 10 m/s^2 due to gravity on Earth
• Parachute stages:

  • Free fall acceleration
  • Increased air resistance, deceleration
  • Terminal velocity, balanced forces
  • Landing, reaction force from the ground
• Levers have input (effort) and output (load) forces

  • Fulcrum is the pivot point
  • Three classes of levers: first, second, third
• Principle of moments: sum of clockwise and anti-clockwise moments is equal at equilibrium

  • Moments = force x perpendicular distance from fulcrum
• Hooke's Law: extension of a spring is directly proportional to force within elastic limit

  • F = kx, k is spring constant
• Density = mass / volume (kg/m^3)

  • Buoyancy: object floats if buoyant force > weight
  • Relative density: ratio of substance density to medium density
• Archimedes principle: buoyant force = weight of fluid displaced
• Distance is scalar, displacement is vector

  • Distance is total ground covered, displacement is change in position
• Displacement is the shortest distance in a straight line between the origin and the destination
• Displacement is a vector because it has only one particular direction
• Velocity is represented by the gradient in a displacement-time graph
• Speed is distance per unit time and is a scalar
• Velocity is displacement per unit time and is a vector
• To convert kilometers per hour to meters per second: multiply by 1000 and divide by 3600
• Newton's second law states that force is equal to mass times acceleration
• Newton's first law states that an object at rest remains at rest, and an object in motion remains in motion at a constant velocity unless acted upon by an unbalanced force
• Acceleration is a change in velocity over time, measured in meters per second squared
• Linear momentum is the product of mass and velocity for an object traveling in a straight line
• To convert meters per second to kilometers per hour: divide by 1000 and multiply by 3600
• Newton's third law states that every action force has an equal and opposite reaction force
• Impulse is the force that produces a change in momentum
• The law of conservation of linear momentum states that the total momentum before collision is equal to the total momentum after collision
• Energy is the capacity for doing work, measured in joules
• The law of conservation of energy states that energy can neither be created nor destroyed, only converted from one form to another
• Efficiency is the ratio of useful output compared to total supplied input
• Kinetic energy is the energy possessed by an object in motion, calculated as 0.5 * mass * velocity^2
• Gravitational potential energy is the energy possessed by an object due to its position or height, calculated as mass * gravity * height
• Work is the energy used to produce a mechanical change, measured in joules
• Power is the rate of energy conversion, measured in watts or joules per second
• Pressure is force acting per unit area, measured in pascals or newton per meter squared