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• Physics is derived from the Greek word "Physikos" which means knowledge of nature.
• Physics aims to understand the world and explain the universe's fundamental nature.
• Questions such as "why?" and "how?" can help in understanding the mysteries of the universe.
• Physics principles explain the majority of natural phenomena.

Fields of Study in Physics

• Classical Physics: Includes motion, light, electricity, magnetism, heat, mechanics, fluids, and sound.
• Modern Physics: Encompasses atomic, molecular, electron physics, nuclear physics, particle physics, relativity, quantum theory, and structure.

Importance of Physics

• Physics is important in science such as astronomy, biology, chemistry, and geology.
• Physics is used in practical developments in engineering, medicine, and other technology.
• Physics research enables studies of radioactive materials, diagnosis, and treatment of certain diseases.

Contributions of Physics

• 1896-98: Discovery of radioactivity.
• 1897: Discovery of the electron.
• 1900: Discovery of quantum energy.
• 1901: Electromagnetic waves were transmitted across the Atlantic Ocean via transatlantic telegraph cables.
• 1905: The Theory of Relativity was discovered.

Physical Quantities

• Speed and velocity are examples of physical quantities that can be measured.
• Physical quantities consist of a numerical magnitude and a unit.
• Every letter of the alphabet is used to represent physical quantities.
• Letters without context are meaningless.
• A physical quantity must contain both a numerical value and a unit.
• Units provide the context as to what a variable refers to.
• If v represents velocity, the unit is m s⁻¹.
• If v represents volume, the unit is m³.
• If v represents voltage, the unit is V.

Estimating Physical Quantities

• Knowing these physical quantities is useful when making estimates.
• Diameter of an atom: 10⁻¹⁰ m
• Wavelength of UV light: 10 nm
• Height of an adult human: 2 m
• Distance between the Earth and the Sun (1 AU): 1.5 x 10⁸ m
• Mass of a hydrogen atom: 10⁻²⁷ kg
• Mass of an adult human: 70 kg
• Mass of a car: 1000 kg
• Seconds in a day: 90000 s
• Seconds in a year: 3 x 10⁷ s
• Speed of sound in air: 300 ms⁻¹
• Power of a lightbulb: 60W
• Atmospheric pressure: 1 x 10⁵ Pa

SI Units

• Physics contains an endless number of units.
• Units can be reduced to base units
• The seven base units are the only measurement system that is officially used.
• Mass: kilogram (kg)
• Length: metre (m)
• Time: second (s)
• Current: ampere (A)
• Temperature: kelvin (K)
• Amount of substance: mole (mol)

Derived Units

• Derived units come from the seven SI Base units. These include:
• Newtons (N)
• Joules (J)
• Pascals (Pa)
• To deduce the base units, the definition of the quantity is necessary
• The Newton (N) is the unit of force, defined as: Force = mass × acceleration or N = kg x m s⁻² .
• In SI base units, the Newton is kg m s⁻².
• The Joule (J) is the unit of energy: Energy = 1/2 × mass × velocity².
• J = kg × (m s⁻¹)² = kg m² s⁻².
• In SI base units, the Joule is kg m² s⁻².
• The Pascal (Pa) is the unit of pressure: Pressure = force ÷ area and Pa = N ÷ m² = (kg m s⁻²) ÷ m² = kg m⁻¹ s⁻².
• In SI base units, the Pascal is kg m⁻¹ s⁻².

Homogeneity of Physical Equations

• Checking the homogeneity of physical equations requires using the SI base units.
• The units on either side of the equation should be the same.
• To check homogeneity:
• Check the units on both sides of an equation.
• Determine if they are equal. If not, the equation should be adjusted.
• Strain (deformation): Strain is defined as "deformation of a solid due to stress".
• Normal strain is the elongation or contraction of a line segment.
• Shear strain is the change in angle between two line segments originally perpendicular.
• Normal strain can be expressed as:
• ε = dl / lo
• dl = change of length (m, in)
• lo = initial length (m, in) ε = strain - unit-less

Prefixes/Powers of Ten

• TERA- (T): 10¹²
• GIGA- (G): 10⁹
• MEGA- (M): 10⁶
• KILO- (k): 10³
• CENTI- (c): 10⁻²
• MILLI- (m): 10⁻³
• MICRO- (μ): 10⁻⁶
• NANO- (n): 10⁻⁹
• PICO- (p): 10⁻¹²
• Writing a normal number with prefixes requires dividing the number by the value of the prefixes
• For instance, converting 0.255 seconds to milliseconds: 0.255 s = 0.255 ÷ 10⁻³ = 255 ms

Scalars & Vectors

• A scalar is a quantity with only magnitude (size).
• A vector is a quantity with both magnitude and direction.
• Distance is a scalar quantity that describes how far an object has traveled overall, without indicating direction.
• Displacement is a vector quantity, describing how far an object is from its starting point and in what direction.

Combining Vectors

• Vectors are represented by an arrow.
• The arrowhead indicates the direction, and the length represents the magnitude.
• Vectors can be combined by adding or subtracting them.
• Two methods to combine vectors: the triangle method and the parallelogram method.
• Triangle method:
• Step 1: Link the vectors head-to-tail.
• Step 2: Form the resultant vector by connecting the tail of the first vector to the head of the second vector.
• Parallelogram method:
• Step 1: Link the vectors tail-to-tail.
• Step 2: Complete the resulting parallelogram.
• Step 3: Resulatant vector is the diagonal of the parallelogram.
• The resultant vector is also formed when two or more vectors are added together (or one is subtracted from the other).

Resolving Vectors

• Two vectors can be represented by a single resultant vector that has the same effect.
• A single resultant vector can be resolved and represented by two vectors, which in combination have the same effect as the original one.
• Parts of a single resultant vector are called components when broken down.
• A force vector of magnitude F and an angle of θ to the horizontal:
• It is possible to resolve this vector into its horizontal and vertical components using trigonometry.
• Horizontal component: Fx = Fcosθ
• Vertical component: Fy = Fsinθ
• The magnitude of A: A = √(Ax² + Ay²)
• The direction of A: tan θ = Ay / Ax; θ = tan⁻¹(Ay / Ax)

Measurements & Error

• Measurement Technique:
• Metre ruler measures distance and length.
• Balances measure mass.
• Protractors measure angles.
• Stopwatches measure time.
• Ammeters measure current.
• Voltmeters measure potential difference.
• Micrometer screw gauge and Vernier calipers can accurately measure ength.
• Instruments and Typical Resolutions:
• Metre rule: 1 mm
• Vernier Calipers: 0.05 mm
• Micrometer: 0.001 mm
• Top-pan Balance: 0.01 g
• Protractor: 1°
• Stopwatch: 0.01 s
• Thermometer: 1°C
• Voltmeter: 1mV - 0.1V
• Ammeter: 1mA - 0.1A

Error

• Measurements aim to find the true value of a quantity.
• In reality, true value is impossible to obtain and there is uncertainty.
• Uncertainty is an estimate of the difference between a reading and the true value.
• Random and systematic errors are two types of measurement erros that lead to uncertainty

Types of Random Errors

• Random: cause unpredictable fluctuations in instrument readings due to uncontrollable factors like environmental changes.
• repeating measurements and averaging them reduces randomness.

Types of Systematic Errors

• Systematic: Related to use of faulty instuments affecting the accuracy of readings obtained.
• Adjusting/recalibrating the equipment can reduce/eliminate systematic errors.
• Zero Error - instrument gives a reading when the true reading is zero.

Precision and Accuracy

• Precision: How close the measured values are to each other in repeated measurements
• Reflected in more decimal places of the measurements.
• Accuracy: How close a measured value is to the true value. Can be increased by repeating meaurements and taking the average.

Uncertainty

• Degree of uncertainty always exists when measurements are taken.
• Uncertainty differs from the true value.
• Measurements within which the true value is expected to lie, is an estiimate.
• Types:
• Absolute Uncertainty: where uncertainty is given as a fixed quantity
• Fractional Uncertainty: given as a fraction of the measurement
• Percentage Uncertainty: give as a percenage of the measurement
• Percentage uncertainty = (uncertainty/measured value) * 100