Physics Study Guide - Matter, Forces and Energy PDF

Matter Nature of matter: the chemical elements, structure of atoms, molecules; Matter refers to everything which occupies space, and has mass which exists in one of three physical states, solid, liquid and gaseous. Simplest form of matter are elements. Elements are made up of atoms. Atoms made...

Matter Nature of matter: the chemical elements, structure of atoms, molecules; Matter refers to everything which occupies space, and has mass which exists in one of three physical states, solid, liquid and gaseous. Simplest form of matter are elements. Elements are made up of atoms. Atoms made up of protons and neutrons with one or more shells of electrons with a dense nucleus. Protons positive electric charge. Electrons negative electric charge. All atoms follow this rule: Maximum number of electrons possible in each shell = 2n2 where n is the shell number. Ions -- Atoms which have lost or gained an electron during a process. Lose an electron become positive, gain an electron become negative. Isotopes -- Atoms of the same element with different number of neutrons **Chemical Compounds** 109 know elements. Most of the matter around us has been formed by one or more elements combining creating compounds. A **compound** is matter in which all the molecules are identical, but the molecules are comprised of different atoms in exact proportions. Chemically bonding when atoms bond together. Transfer electrons from molecules Mixtures - two or more substances where each substance retains it own individual characteristics. E.g Salty water **States: solid, liquid and gaseous;** All atoms and molecules in matter are constantly in vibratory motion. The degree of motion i.e. the internal kinetic energy possessed by the matter, determines its physical state. This internal KE is what we know as heat. Solids - A solid has a definite volume and shape and is independent of its container. Very little heat energy so atoms can't move far from their relative position making them incompressible. Liquids -- When heat is added to solid matter its molecular movement increases causing it to become a liquid. Volume doesn't change from solid to liquid. Conforms to the shape of a container. Incompressible Have definite volume but no shape Molecules are still partially bonded together this is called surface tension. Gas -- As heat is continually added molecular movement increases until the liquid reaches a point where surface tension can no longer hold the molecules down. Molecules escape becoming gas or vapour. Have no shape or volume and are compressible **Topic 2: Statics** **Forces, moments and couples, representation as vectors;** A force can be described as that which can produce a change in a body's state of motion. An application of force will: Start, stop, accelerate, or decelerate a mass. If **energy** is available, then forces can be used to do **work**. When an object does not change its state of motion or rest, **the resultant of all the** **forces acting on it is zero,** and it is said to be in a state of **equilibrium**. A lever is an example of a **Simple Machine**, which is a device used to gain a **Mechanical Advantage, MA,** **MA = Load/Effort** An example of a **first-class lever** is a **CROWBAR** **Second-class lever** - cockpit control levers, such as a throttle or thrust lever, and a simple wheelbarrow. **Third-class lever --** Landing gear A **Velocity Ratio** is the direct ratio of two speeds that may be present in the same system. Forces acting on a stationary body are measured in pounds or newtons. Couple A **'couple'** is a type of moment which is derived from **two equal forces acting in** **parallel but opposite directions on two different points of a body.** A **moment** is the distance between an applied force and a reference point. If the effort moment is greater than the load moment the load will be raised. Centre of Gravity The centre of gravity (CG) of an aircraft is the balance point for the aircraft. **Elements of theory of stress, strain and elasticity: tension, compression, shear and torsion;** **Stress** is the force acting through a section of solid material and defined as **force per unit area.** **Strain** is the **deformation** of the material as a **result of the stress.** If strain is less than materials elastic limit it will return back to normal. Strain below the elastic limit is directly proportional to the applied stress (Hooke's Law). **Tension** is the stress that resists a force that tends to pull something apart. **Compression** is the stress that resists a crushing force.  Aircraft riveting is performed using **compressive forces**. **Shear** stresses occur when external forces distort a body so that adjacent layers of material tend to slide over one another. Shear stress may also occur in **fluids**. **Torsion** is the stress that resists twisting.  **Residual Stress ("Locked In Stress")** is Abrupt or uneven temperature changes tend to cause internal stress. Often occurs when heat treating materials. **Aerodynamic and gravitational forces** try to bend the wing or blade upwards and downwards. Consequently, the top and bottom surfaces of the wing are under **alternating compression and tensile stresses** and must be constructed to withstand the fatigue that could develop from this situation. **Pressure and buoyancy in liquids (barometers).** **Both liquids and gases are fluids, therefore the theory behind buoyancy and pressure** **in liquids, such as water, and gases, such as air, is similar.** **Liquids are considered incompressible, that is, have a constant density, while gases are compressible.** **Pressure in fluids** The pressure exerted by a column of liquid is determined by the vertical **height of the** **column, gravity, and the density of the fluid.** **The pressure** is not affected by the volume or shape of the liquid. **Density and Specific Gravity** **Density** is defined as the **mass per unit volume** of a substance. When the density of other liquids are compared to water, a table of **comparative** **densities or specific gravities** can be determined. **Gasoline** has a specific gravity of 0.72, which means its weight is **72% of the same** **amount of water.** Specific gravity of aviation fuel varies due to : **Refining process, storage facilities and ambient conditions** Buoyancy **Archimedes principle** states that an item placed in fluid will displace a volume of fluid equal to its own volume. Furthermore, the object submerged in the fluid is supported by a force equal to the weight of the fluid displaced. This is the **buoyancy force.** Therefore if a body displaces more fluid than its own weight it will float. **Solids** have a definite shape and a definite volume which is independent of its container. Both liquids and gases are classified as **fluids**. **Pascal's law** states ,that when pressure is applied to a **confined liquid, the liquid exerts an equal pressure at right angles** to the container that encloses it **Solids** have a definite shape and a definite volume which is independent of its container 2.2.2 Kinetics Displacement and Distance The aircraft may travel a **total distance of 2 km** as it veers left and right, but its **displacement**, measured only as the difference between the start point and finish point, will be less. Speed and Velocity A similar distinction can be made between **speed** and **velocity**. They both refer to the **distance travelled per unit of time**, for example, miles per hour, metres per second etc. Acceleration When an object has an initial velocity then, after a period of time, that velocity has changed (increased or decreased), the object is said to have **accelerated**. Acceleration can be positive or negative. Negative acceleration is called **deceleration**. Acceleration is the **rate of change in velocity.** You will remember that force is defined as that which uses energy to produce a change in motion state. **NEWTON** explored this and formulated his three famous Laws. 1. **A body will remain at rest or continue its uniform motion in a straight line until** **acted upon by an external net force** This law is a statement about **INERTIA** which is the property of mass that **resists** **changes in motion.** 2. **The acceleration of a body is directly proportional to the force applied to it and** **is inversely proportional to the mass of the body.** This law is represented by the formula: **F = ma** 3. **For every action, there is an equal and opposite reaction.** Stand on a skate board and throw a large mass away from yourself, and you will roll in the opposite direction. CIRCULAR MOTION In accordance with Newton's First Law, the object would shoot off on a straight path unless a **Centripetal Force is continually applied** to keep it turning along the curve. Periodic Motion **Periodic motion** or simple harmonic motion refers to repeated motion. The energy contained in a body moving with SHM is called **wave energy.** **Vibration** is a term normally reserved for high frequency periodic motion. Also, the structure of the aircraft and other components can vibrate in sympathy and **structural damage and component wear can occur.** **Metal fatigue** is an example of such structural damage. Vibration experienced in an aircraft may originate from the **engines, turbulence, or** **from flight control flutter** due to worn hinges or linkage bearings. RESONANCE If two objects have the same natural frequency and are joined to each other, when one of them vibrates, it can **transfer its wave energy to the other object** making it vibrate. This transfer of energy is known as **Resonance.** HARMONICS Harmonics exist as **multiples** of an original, natural frequency. That is, if the natural frequency is 100 Hz: the 1st harmonic is at 200 Hz and the 2nd harmonic is at 300 Hz etc **Topic 2.3 Dynamics** Inertia Inertia is the property of a mass which causes it to **resist any change in its state of** **Motion.** Newton's first law of motion states: A body will remain at rest or continue its uniform motion in a straight line until acted upon by an external net force. The larger the mass, the greater the inertia. Work When a force acts on an object and overcomes inertia **work** is done. **W=FS F = Force S = Distance** Unit of work is the **joule** which equals **1 newton metre (NM)** If an object is moved 10 metres by a force of 100 newtons, the work is calculated as: W = Fs W = 100 x 10 (Nm) W = 1 000 joules. In the Imperial system of measurement, a measure of work is the **foot-pound**, the effort of raising one pound of mass by one foot. POWER Power is the rate of doing work. When determining the amount of work done, the time required to do the work is not considered. Power on the other hand takes time into consideration. For example, if a person climbs a flight of stairs, they perform the same amount of work whether they walk up or run up. However, when the person runs up they are working at a **faster rate** and therefore using **more power**. The unit SI unit of power is the **watt**. In the imperial system of measurement, power is expressed in **foot/pounds per second** and **one horsepower** is equivalent to 550 foot/pounds per second and 746 Watts. ENERGY The SI unit of energy us **joule**. law of the conservation of energy which states: **Energy can neither be created nor destroyed. It can only be changed from one form** **to another.** For example, a car turns the **chemical energy** found in petrol into **mechanical energy,** **heat and sound.** Potential Energy The potential energy in a body or of a body means **stored energy**, stored in the body because of its **position, condition or chemical nature.**  Kinetic Energy Kinetic energy is energy a body has **because of its motion**. If a body is held aloft and then released, as it starts to fall to ground the **potential energy is converted to kinetic energy**. Total Energy In accordance with the law of conservation of energy, **the total energy does not** **change**, but potential energy can be transformed into kinetic energy and vice-versa. Friction When objects move they usually roll or slide in contact with other objects or substances. Such sliding or rolling contacts have resistance to the force that causes the motion. This resistance is called **friction**. The **coefficient of friction** refers to the **differences in friction between various** **materials.** **Lubrication** reduces friction. Three types: Starting, Sliding, Rolling Rolling one surface over another creates less friction than sliding one surface over another. Heat Heat is one of the most useful forms of energy because of its direct relationship with work, and with the use of engines. **Heat is also found as a consequence of friction. The heat produced by friction is** **usually unwanted.** **Efficiency** **With any machinery, the efficiency is the ratio of work output to worker energy input.** **Efficiency = Work out / Work in X 100** **It is friction that primarily determines the efficiency of a machine, because the friction between moving parts creates heat, sound and sometimes light.** **Reducing friction is usually accomplished by lubrication or streamlining.** **Momentum** **There are two types of momentum, linear and angular.** **Linear momentum is a measure of the tendency of a moving body to continue in motion along a straight line.** **Angular momentum is a measure of the tendency of a rotating body** **to continue to spin about an axis.** **IMPULSE** **If a force is applied to a moving body, that body's state of motion is altered.** **A SIMPLE GYROSCOPE** **A gyroscope is any rotating mass.** **Gyroscope has two fundamental characteristics. These are gyroscopic** **inertia (rigidity in space) and precession.** **Gyroscopic rigidity** **This the natural property of any rotating mass to resist changes to its plane of rotation unless an external force causes a change.** **This is the reason a spinning top or coin remains upright until it runs down.** **Precession** **This the change of the plane of rotation caused by an external force.** **Topic 2.4 Fluid Dynamics** **A liquid is difficult to compress and often regarded as being Incompressible.** **A gas is easily to compress and usually treated as such - it changes volume with pressure** **Viscosity** **Defined as the resistance of fluid flow.** **Thick oil is more resistant to flow than light sewing machine oil, so is more viscous.** **Air must possess a small amount of viscosity, otherwise there would be no resistance to airflow to provide aerodynamic force.** **Viscosity Index** The **viscosity index** of a fluid is a measure of the change in the **viscosity of a fluid with a change in its temperature.** For most liquids, viscosity decreases with increasing temperature. For lubricating oils used in aircraft, a **low viscosity** index is good because this means the properties of the oil will not change much over a wide range of operating temperatures. Temperature of gas increases viscosity increases. Properties of Fluid Flow A **fluid can turn reasonable corners**, as shown around this balloon, and this is the **Coanda Effect.** Tendency of fluid to stay attached to a convex surface. The region of flow in which the speed is reduced is called the **Boundary Layer.** The shape of an object in airflow is crucial. If the curvature **is low enough**, the Coanda effect can occur and the flow remains attached. **If not, the flow separates and air** **resistance or drag is high.** STATIC, DYNAMIC AND TOTAL PRESSURE During aircraft flight, the plane travels through a fluid (air) which has a certain Atmospheric or Static pressure, (P), due to the weight of the atmosphere above it. The aeroplane also has forward, dynamic, motion which means that it is striking air molecules at a rate proportional to its speed. creating a **dynamic pressure.** BERNOULLI'S THEOREM Bernoulli\'s principle formulated by **Daniel Bernoulli** states that as the **speed of a moving fluid increases (liquid or gas), the pressure within the fluid decreases.** This reduction of static pressure through a constriction is called the **Venturi Effect** and is represented by the Bernoulli Theorem equation: Static Pressure + Dynamic Pressure = Constant (Total Pressure) An extension of Bernoulli's Theorem is the basis of how some of the lift is generated by aircraft **wings, propellers and helicopter rotor blades.** The air passing over **the top surface of the wing moves at a higher velocity**. The **higher velocity causes a decreased press**ure there, and a pressure difference between upper and lower wing surfaces contributes to the force known as '**lift'**. TOPIC 3: THERMODYNAMICS The **Conservation of Energy** states that energy cannot be created or destroyed, only converted from one form to another. Energy concerning the application, **loss or transfer of heat is termed thermal energy.** According to the law of conservation of energy, **thermal energy cannot be created or destroyed, but it is converted from, and to, other forms of energy.** Thermal energy can be created from electrical, mechanical, chemical and nuclear. Heat Transfer **Conduction** requires **physical contact** between a body having a high level of heat energy and a body having a lower level of heat energy. When a cold object comes into contact with a hotter object, the action of the molecules in the hot material **transfers some of their energy** to the molecules in the colder material. Convection Convection is the process by which heat is transferred by bulk movement of fluid. As fluid is **heated** by a heat source, it **becomes less dense and rises**, being replaced by cooler fluid. **Heating water in a kettle, heating air in a house** and the **circulation of atmospheric heat are examples of convection.** Units of heat **Calorie (cal)** - one calorie is the quantity of heat required to raise the temperature of one gram of water by one degree Celsius. **British thermal unit (btu)** - one Btu is the quantity of heat required to raise the temperature of one pound of water by on degree Fahrenheit. **Joule** - the SI unit for all forms of energy. **Energy provides the capacity for work to be done.** One joule of energy can do one joule of work. Specific heat and Heat Capacity The specific heat of a substance is the number of calories required to raise the temperature of 1 gram of the substance by 1°C or, the number of Btu's required to raise the temperature of 1 pound of the substance by 1°F. Water is used as the benchmark as it takes 1 calorie to raise 1 gram of water by 1°C. The heat capacity C of a substance is the amount of heat required to change its temperature by one degree, and has units of energy per degree. LATENT and SENSIBLE HEAT **Latent heat** is when no temperature change occurs during a change of state even though heat was added. The amount of heat required to boil, or vaporise, the liquid is called the **latent heat of** **vaporisation (or evaporation).** The amount of heat required to **melt** a solid is called the **latent heat of fusion.** **Sensible heat is** heat, when applied, **causes a temperature change** that can be detected. Latent heat is used to **break down intermolecular bonds**, and sensible heat is **stored** **in intermolecular forces,** increasing kinetic energy of the molecules. GAS LAWS It has been stated that gasses differ from solids and liquids by being compressible. This affects how they transmit forces that can use the thermal energy to effect change by doing useful work. Boyles Law As a gas is **compressed its** **pressure increases** and **volume decreases**. Assuming the **temp remains constant.** If the volume is halved, the pressure doubles. Charles Law Charles' Law which states that the volume of a gas **varies in direct proportion to its temperature**, assuming pressure remains constant. Doubling the temperature will double the volume. The temperature change could occur without the addition of **external heat, or removal of heat by external means. This is called an adiabatic process.** General gas law The general gas law is derived by combining **Boyle's and Charles' laws.** THERMAL ENERGY and LAWS OF THERMODYNAMICS The **first law of thermodynamics**: Heat energy cannot be destroyed, it can only be changed from one form of energy to another. For example, the **heat energy** of combustion in an engine is **transformed into mechanical energy**, but there are losses or inefficiencies as some of the energy is **transformed to sound energy.** The **second law of thermodynamics** states that heat cannot flow from a body of a given temperature to a body of a higher temperature. That is, **heat will only flow from** **a warmer body to a cooler body.** This is a logical process and the theory behind it is used in **car radiators, heat exchangers, oil coolers etc.** HEAT OF COMBUSTION Any time fuel is burnt **(combustion), heat is produced.** Sometimes heat is useful sometimes not. We say heat is the **by product** of the combustion process. Combustion can use **liquid, solid or gaseous** fuel. Often **heat** is wasted and **needs to be dissipated** for the engine to work optimally. E.g most cars have **water** circulating the engine. The water is cooled by the **radiator**. In a gas turbine (jet) engine, the heat of combustion is necessary to expand gases and do work while flowing through the engine. **A gas turbine engine relies on heat to expand gas**. The expanded volume of gas drives the engine turbines and contributes to the reactive force of thrust. Remember, work is calculated by multiplying the force applied by distance: **W = Fs.** **The greater the force** applied to an object or **the greater the distance** an object moves, **the more work has been done.** If expanding gases in a rifle create a force of 10,000 newtons and move a bullet 0.5 metres along the barrel of the rifle: **W = Fs** = 10,000 x 0.5 = 5,000 **joules of work has been expended.** Remember, also, that power is the time **rate of doing work.** A man may expend 5,000 joules pushing a wheelbarrow for **1 hour**. The rifle has expended the **5,000 joules in a split second**. It has generated a great deal **more power** than the wheelbarrow man. TOPIC 4: OPTICS (LIGHT) The nature of light Visible light is Electromagnetic Radiation that is **detectable by the human eye.** Speed of light The speed of EMR propagation c, commonly called the speed of light is **3 x 108 m/s in** **a vacuum. (300,000 km/s or 186,000 mph.)** Light is assumed to be **wave-based,** but there is also evidence that light is composed **of particles with mass. (photons).** Some of the evidence that light is composed of waves is:  Light can be reflected and refracted;  Light can be dispersed, broken down into spectral components meaning that each colour has a different wavelength;  Polarisation and Polaroid lenses blocking out one plane of light waves;  Light experiences a Doppler effect (red shift). Reflection of light **Reflection** of light and other electromagnetic radiation occurs when waves encounter a boundary that **does not absorb the radiation's energy** and bounces the waves off the surface. The incoming wave is known as the **incident wave** and the wave that is bounced from the surface is called the **reflected wave**. T**he law of reflection states that the angle of incidence equals the angle of reflection.**  REFRACTION The angle of refraction is dependent on **the density of the material** through which the light passes. For example, when light travels from air to water, **it slows down** and bends towards the normal. Most substances have a **refraction index.** The h**igher the refraction index the denser the material.** Dispersion The index of refraction also varies with the **wavelength** of the radiation. If white light enters a prism, the different wavelengths of the component colours are refracted by different amounts. This is termed **dispersion**.