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Questions and Answers
What effect do smaller 'grains' have on metals?
What effect do smaller 'grains' have on metals?
Glass has a plastic region in its stress-strain curve.
Glass has a plastic region in its stress-strain curve.
False (B)
What defines the behavior of a polymer?
What defines the behavior of a polymer?
The number and strength of cross-links between molecules.
The ultimate breaking stress of glass is about ______ MPa.
The ultimate breaking stress of glass is about ______ MPa.
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Which material is categorized as brittle?
Which material is categorized as brittle?
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Match the following materials with their characteristics:
Match the following materials with their characteristics:
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The mechanical properties of rubber improve when impurities like sulfur are added.
The mechanical properties of rubber improve when impurities like sulfur are added.
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What type of bonds are mainly responsible for the strength of cross-links in polymers?
What type of bonds are mainly responsible for the strength of cross-links in polymers?
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What occurs when a metal is extended beyond its elastic limit?
What occurs when a metal is extended beyond its elastic limit?
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Necking occurs when a material becomes narrower and extends rapidly just before breaking.
Necking occurs when a material becomes narrower and extends rapidly just before breaking.
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What are edge dislocations?
What are edge dislocations?
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When stress is applied to a metal and it behaves elastically, the relationship followed is _____ (use the symbol).
When stress is applied to a metal and it behaves elastically, the relationship followed is _____ (use the symbol).
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What is the ultimate tensile strength of a material used to indicate?
What is the ultimate tensile strength of a material used to indicate?
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Crystalline materials transmit forces equally due to their random atomic arrangement.
Crystalline materials transmit forces equally due to their random atomic arrangement.
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Match the type of solid to its description:
Match the type of solid to its description:
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The phenomenon where atoms in one plane slip over atoms in another plane is called _____ .
The phenomenon where atoms in one plane slip over atoms in another plane is called _____ .
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What does Young's Modulus indicate?
What does Young's Modulus indicate?
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Crystalline solids exhibit long-range order in their atomic arrangement.
Crystalline solids exhibit long-range order in their atomic arrangement.
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Name an example of an amorphous solid.
Name an example of an amorphous solid.
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The line between grains in polycrystalline solids is known as the ______.
The line between grains in polycrystalline solids is known as the ______.
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At which point in the stress-strain graph does the material return to its original shape after the force is removed?
At which point in the stress-strain graph does the material return to its original shape after the force is removed?
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Match the type of solid with its characteristics:
Match the type of solid with its characteristics:
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The stress-strain relationship is linear until the yield point is reached.
The stress-strain relationship is linear until the yield point is reached.
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What happens to the material after reaching the yield point?
What happens to the material after reaching the yield point?
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Study Notes
WJEC AS-1 Physics Revision Notes
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Unit 1: Motion, Energy and Matter
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1.1 Basic Physics
- 1.1.1 SI Units: All physical quantities have magnitude and a unit. SI units are a set of internationally agreed units for physics quantities. Examples include: coulomb (C) for charge, newton (N) for force, and joule (J) for energy.
- 1.1.2 Prefixes and Standard Form: Quantities can be very large or small, using prefixes and standard form helps with these. Examples of prefixes: Tera (T), Giga (G), Mega (M), Kilo (k), Centi (c), Milli (m), Micro (µ), Nano (n), Pico (p), and Femto (f).
- 1.1.3 Scalars and Vectors: Scalars have magnitude only (e.g., mass, distance, time, speed). Vectors have magnitude and direction (e.g., displacement, velocity, force, current). Vectors can be added and subtracted using trigonometry.
- 1.1.4 Density: Density is mass per unit volume. Units are kg/m³. Density of common substances varies considerably. Gases have low density, liquids intermediate, and solids high.
- 1.1.5 Moments (Turning Effect/Torque): Moment of a force (turning effect/torque) is force × perpendicular distance from pivot. Essential for equilibrium calculations.
- 1.1.6 Bodies in Equilibrium: Two conditions of equilibrium: resultant force = 0, and net moment = 0.
- 1.1.7 Centre of Gravity: The point at which the weight of an object appears to act. Crucial for calculations on toppling, stability, and moments.
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1.2 Kinematics
- 1.2.1 Motion: Definitions of displacement, velocity, speed, acceleration are critical. Key equations show relationships between these.
- 1.2.2 Motion Graphs (Displacement-Time Graphs): The gradient of a displacement-time graph gives velocity. The area under the graph gives displacement travelled.
- 1.2.3 Motion Graphs (Velocity-Time Graphs): The gradient of a velocity-time graph gives acceleration, the area gives displacement.
- 1.2.4 Falling Objects – Vertical Motion Under Gravity: Acceleration due to gravity, air resistance impact.
- 1.2.5 Projectile Motion: Path of a projectile (thrown object) is parabolic. The horizontal and vertical components have independent motion.
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1.3 Dynamics
- 1.3.1 Newton's Laws of Motion: Newton's first law, inertia; second law (F = ma), and third law (action-reaction).
- 1.3.2 Newton's 3rd Law: Action-reaction forces are equal in magnitude but opposite in direction.
- 1.3.3 Momentum: Momentum = mass × velocity (kg m/s). Momentum is conserved in collisions (unless external forces act).
- 1.3.4 Elastic and Inelastic Collisions: Elastic collisions conserve kinetic energy, inelastic collisions do not.
- 1.3.5 Newton's 2nd Law: Rate of change of momentum is proportional to the resultant force.
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1.4 Energy Concepts
- 1.4.1 Work: Work done = force × distance moved along the line of force. Measured in joules (J).
- 1.4.2 Energy: The capacity to do work Energy is measured in joules. Different forms: kinetic, gravitational potential, elastic potential.
- 1.4.3 The Work-Energy Relationship: Work done results in a change in energy, typically a change in kinetic energy.
- 1.4.4 Power: Power is the rate of doing work or transferring energy (joules/second = watts).
- 1.4.5 Dissipative Forces and Energy: Forces like friction convert kinetic energy into thermal energy, reducing efficiency.
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1.5 Solids Under Stress
- 1.5.1 Forces on Solid Materials: Compressive, tensile, and shear forces affect solids.
- 1.5.2 Hooke's Law: Extension of a spring is proportional to the applied force, provided the limit of proportionality is not exceeded. F = kx, where k is constant.
- 1.5.3 Springs in Series and Parallel: Combinations of springs in series or parallel exhibit unique behaviours.
- 1.5.4 Work of Deformation and Strain Energy: Work done in deforming a material is stored as elastic potential energy.
- 1.5.5 Stress, Strain, and Young's Modulus: Stress is defined as force over cross-sectional area; strain is the change in length divided by original length; Young's modulus relates stress and strain.
- 1.5.6 Types of Solids: Different types of solids (crystalline and amorphous) have different structural properties.
- 1.5.7 Stress-Strain Graphs for Metals: Important points on a stress-strain curve: limit of proportionality, elastic limit, yield point, ultimate tensile stress, fracture.
- 1.5.8 Brittle Materials and Rubber: Stress-strain curves for brittle materials and rubber show their distinctive behaviour and the importance of cross-links for flexibility.
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1.6 Using Radiation to Investigate Stars
- 1.6.1 Stellar Spectra and Black Bodies: Stars emit radiation across the EM spectrum, allowing investigation. Black bodies are ideal emitters of radiation and their spectra depend only on their temperature.
- 1.6.2 Wien's Law: The peak wavelength of a black body is inversely proportional to its temperature.
- 1.6.3 Stephan-Boltzmann Law: The power emitted by a black body is proportional to the fourth power of its temperature.
- 1.6.4 Luminosity, Intensity, and Distance: Luminosity is the total energy emitted by a star per unit time; intensity is power per unit area, and decreases with distance from the star.
- 1.6.5 Multiwavelength Astronomy: Observing stars across different parts of the electromagnetic spectrum provides comprehensive info. about stars and the universe.
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1.7 Particles and Nuclear Structure
- 1.7.1 A Brief History of Our Understanding of the Atom: Development of atomic models over time, including the discovery of electrons and the nucleus.
- 1.7.2 Quarks and Leptons: Subatomic particles like quarks and leptons form more complex particles.
- 1.7.3 Hadrons: Hadrons (protons, neutrons, mesons). Important characteristics of these include quark composition.
- 1.7.4 Interactions (Forces) Between Particles: Four fundamental forces (gravitational, electromagnetic, strong, and weak); range, relative strengths affect particle behaviour.
- 1.7.5 Conservation Laws: Fundamental quantities (charge, lepton number, baryon number) are conserved in particle interactions.
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