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Questions and Answers
What is the significance of the condition where the net force on an object is zero?
What is the significance of the condition where the net force on an object is zero?
Which of the following correctly describes the relationship defined by Newton's second law of motion?
Which of the following correctly describes the relationship defined by Newton's second law of motion?
What occurs when balanced forces act on an object?
What occurs when balanced forces act on an object?
What does the equation $F = \frac{GMm}{r^2}$ represent in terms of gravitational interaction?
What does the equation $F = \frac{GMm}{r^2}$ represent in terms of gravitational interaction?
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What happens when unbalanced forces act on an object?
What happens when unbalanced forces act on an object?
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Which of the following represents a derived quantity?
Which of the following represents a derived quantity?
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What is the standard unit of luminous intensity in the SI system?
What is the standard unit of luminous intensity in the SI system?
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How is one second defined in the context of the cesium atom's oscillations?
How is one second defined in the context of the cesium atom's oscillations?
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In the metric system, what is the relationship between the prefixes and powers of 10?
In the metric system, what is the relationship between the prefixes and powers of 10?
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What is the standard unit of mass as defined in the SI system?
What is the standard unit of mass as defined in the SI system?
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Study Notes
Chapter 1: Principal System of Units
- Physics is an experimental science, a science of measurements.
- Accurate and reproducible measurements are crucial.
- Units are essential for ensuring accuracy and reproducibility.
- Measurement of a quantity is expressed as a number and a unit.
Physical Quantities
- Basic/Fundamental Quantities: Length, Mass, Time, Electric current (ampere), Temperature (Kelvin), Luminous intensity (candela), Amount of substance (mole).
- Derived Quantities: Combinations of basic quantities (e.g., velocity = distance/time, force = mass x acceleration).
- Energy (E) = force x distance
Standards
- Standards are needed to measure any quantity, so standards need to be defined.
- Standards should be durable and have a stable chemical structure.
- Length: The distance between two lines on a platinum-iridium bar (1 meter) or the wavelength of orange-red light from a krypton lamp (1 meter = 1650763.73 λk). Another way to define a meter is the distance light travels in a vacuum in 1/299 792458 of a second.
- Mass: Mass of a platinum-iridium cylinder (1 kilogram).
- Time: The time between successive appearances of the sun ("solar day") or it's 1/86400th of a mean solar day. 1 second is also equal to 1 / 31556925.974 of tropical year or 1/9192631770 oscillations of radiation emitted by cesium atoms.
Systems of Units
- CGS: Centimeter-Gram-Second system
- MKS (SI): Meter-Kilogram-Second system
- fbs (British): Foot-Pound-Second system
- Units must be the same on both sides of an equation.
Multiples and Submultiples (Fractions) of Metric Units
- Prefixes correspond to powers of 10.
- Each prefix has a specific name and abbreviation (e.g., kilo, mega, milli, micro).
Unit Conversion
- Converting units within a system or between different systems.
- Conversion factors are rearranged forms of equalities.
Dimensions
- Dimensions of a physical quantity specify its nature (e.g., length, time, mass, energy).
- Common dimensions include Length [L], Mass [M], and Time [T]
- Different systems of units use different units for the same dimension.
Dimensional Analysis
- Verification/check of physical equations.
- Derivation of relations between physical quantities.
- Determining dimensions of constants.
- Dimensions can be treated as algebraic quantities.
- Quantities are added or subtracted only if their dimensions are the same.
Chapter 2: The Laws of Motion
The Concept of Force
- Force causes changes in motion (acceleration or direction changes).
- A force is a push or pull.
- Forces don't always cause motion (balanced forces).
- The net force on an object is the vector sum of all forces acting on it.
- If the net force = 0, the object is not accelerating (constant velocity or at rest).
- If the net force ≠ 0, the object accelerates.
Balanced and Unbalanced Forces
- Balanced forces: Equal in magnitude, opposite in direction.
- Unbalanced forces: unequal forces, cause acceleration.
Newton's Laws of Motion
- 1st Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion with the same velocity unless acted upon by an unbalanced force.
- 2nd Law (Force = mass x acceleration): The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
- 3rd Law (Action-Reaction): For every action, there is an equal and opposite reaction.
Inertia
- Inertia is an object's resistance to changes in its state of motion (rest or constant velocity).
- Mass is a measure of inertia.
- More mass = more inertia.
Types of Inertia
- Inertia of rest: Resistance to change in its state of rest
- Inertia of motion: Resistance to changes in its state of uniform motion
- Inertia of direction: Resistance to changes in its direction of uniform motion
Mass and Inertia
- Mass: The amount of matter in an object, independent of surroundings or measurement method.
- Units: Kilograms (kg) or grams (gm).
- Inertia: A measure of how an object resists changes in motion. -More mass = more inertia.
Newton's Second Law (Force, Mass, and Acceleration)
- Acceleration is directly proportional to the net force and inversely to the mass.
- Units of force are Newtons (N)
Force of Gravity and Weight
- Gravity is an attractive force between Earth and objects.
- Weight is the magnitude of the force of gravity (w = mg).
- Acceleration due to gravity (g) ≈ 9.8 m/s².
Weight
- Measure of the force of gravity on an object's mass.
- Units are Newtons (N).
Newton's Third Law
- Action-reaction force pairs always act on different objects
- The action force and the reaction force have the same magnitude, but opposite directions .
Forces of Friction
- Friction resists motion between surfaces.
- Friction force is opposite to motion
- Determined by roughness and force pressing surfaces together.
Types of Friction
- Static: Resists start of motion.
- Sliding/Kinetic: Resisting motion when surfaces are sliding against each other.
- Rolling: Resistance opposing rolling motion.
- Fluid: Resistance in liquids or gases.
Coefficients of Friction
- Dimensionless constant
- Depends on the surfaces
- Values vary based on the nature of the surfaces.
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Description
This quiz covers the fundamental principles of measurement in physics as outlined in Chapter 1. Learn about basic and derived physical quantities, the importance of accurate units, and the standards used for measurement. Test your understanding of how these concepts shape experimental science.
