Physics Chapter 1: Measurements and Units

• Chapter 1 is about the Measurement of Physics.
• Syllabus includes measurements of physics, kinematics and dynamics, work energy and power, fluid mechanics, concept of heat and temperature, electricity and magnetism, geometrical optics and physical optics, nucleus and photoelectric effect, sound, and medical physics.
• Final Exam is worth 50% and is made up of Part A with 20 MCQs and Part B with 6 structured questions.
• Continuous Assessment is worth 50% and is made up of lab practical for 10%, quiz 1 for 5%, quiz 2 for 5%, CA 1 (week 6) for 10% including Part A with 10 MCQs and Part B with 4 structured questions, CA 2 (week 12) for 10% including Part A with 10 MCQs and Part B with 4 structured questions, and poster presentations for 10%.

Chapter Outline

• Standard Units
• Physical Quantities
• Accuracy and Precision
• Unit Conversion
• Significant figures

Standard Units

• The SI system is also called the metric system, and is used around the world
• Length SI unit is the meter (m)
• Mass SI unit is the kilogram (kg)
• Time SI unit is the second (s)
• Temperature SI unit is the kelvin (K)
• Electric current SI unit is the ampere (A)
• Amount of substance SI unit is the mole (mol)

Physical Quantities and SI Units

• Physical quantity is defined as a quantity that can be measured using a measuring instrument
• Unit is defined as a standard size of measurement of a physical quantity
• Physical quantity can be categorized into two types: base quantity and derived quantity

Base Quantity

• Base quantity is defined as a quantity that cannot be derived from any other physical quantity.
• Length SI unit is the meter (m)
• Mass SI unit is the kilogram (kg)
• Time SI unit is the second (s)
• Temperature SI unit is the kelvin (K)
• Electric current SI unit is the ampere (A)
• Amount of substance SI unit is the mole (mol)

Derived Quantity

• Derived quantity is defined as a quantity that is obtained from the combination of base quantities.
• Velocity = s/t, measured in m s⁻¹
• Frequency = 1/T, measured in s⁻¹ or Hz (hertz)
• Acceleration = v/t, measured in m s⁻²
• Pressure = F/A, measured in N m⁻² or Pa (pascal)
• Momentum = m x v, measured in kg m s⁻¹
• Force = m x a, measured in kg m s² or N(newton)
• Work = F x s, measured in kg m² s⁻² or J(joule)
• Power = W/t, measured in Js⁻¹ or W (watt)

Accuracy and Precision

• Accuracy measures how close a measurement is to the true value of the quantity being measured.
• Precision measures how close a series of measurements are to one another, and how exact a measurement is.

Sources of Error

• Human error includes mistakes made in reading an instrument or recording the results.
• Method Error happens when measurements are taken using different methods
• Parallax error is an overestimate due to the improper viewing of a measuring device.
• Instrumental error means improperly displayed measurements due to poorly calibrated devices.

Errors

• Systematic error is caused by the equipment used.
• Random error is caused by environmental factors.
• Zero errors are systematic errors.
• Parallax error is a random error.

Precision and Significant Figures

• Significant figures describe the precision of a measuring device.

Guidelines for Using Significant Figures

• Any digit that is not zero is significant, e.g., 845 cm has 3 SFs.
• Zeros between nonzero digits are significant, e.g., 40 501 kg contains 5 SFs.
• Zeros to the left of the first nonzero digit are not significant, e.g., 0.008 L contains 1 SF.
• If the number is ≥ 1, then all the zeros written to the right of the decimal point are significant, e.g., 2.00 mg has 3 SFs.