General Physics

Momentum  An object with that is in motion has momentum which is defined by the equation (Momentum = mass x velocity). 
Kinetic energy  The kinetic energy, E, of an object (also known as its kinetic store) is defined as: K The energy an object has as a result of its mass and speed  This means that any object in motion has energy in its kinetic energy store  Kinetic energy can be calculated using the equation: EK = ½ × m × v2 
Collisions The total momentum before a collision = The total momentum after a collision  Before the collision:  The momentum is only of mass m which is moving  If the right is taken as the positive direction, the total momentum of the system is m × u  After the collision:  Mass M also now has momentum  The velocity of m is now v (since it is now travelling to the left) and the velocity of M is V  The total momentum is now the momentum of M + momentum of m  This is (M × V) + (m × v) or (M × V) – (m × v) 
Gravitational potential energy  The gravitational potential energy, E, of an object (also known as its gravitational store) is defined as: P The energy an object has due to its height in a gravitational field  This means:  If an object is lifted up, energy will be transferred to its gravitational store  If an object falls, energy will be transferred away from its gravitational store  The GPE of an object can be calculated using the equation: ΔEP = mgΔh 
Impulse  When a resultant (unbalanced) force acts on a mass, the momentum of that mass will change  The impulse of a force is equal to that force multiplied by the time for which it acts: impulse = force × change in time impulse = FΔt  The change in momentum of a mass is equal to the impulse provided by the force: impulse = change in momentum impulse = FΔt = Δp  Change in momentum can also be described as: Δp = Δ(mv) Δp = mv − mu  Where:  m = mass in kg  v = final velocity in m/s  u = initial velocity in m/s  Therefore: impulse = FΔt = Δp = mv − mu 
Work done  Work is done when an object is moved over a distance by a force applied in the direction of its displacement  It is said that the force does work on the object  If a force is applied to an object but doesn’t result in any movement, no work is done Work is done when a force is used to move an object  The formula for work done is: Work done = force × distance W = fd 
Energy  Energy is a property that must be transferred to an object in order to perform work on or heat up that object  It is measured in units of Joules (J)  Energy will often be described as part of an energy system  In physics, a system is defined as: An object or group of objects  Therefore, when describing the changes within a system, only the objects or group of objects and the surroundings need to be considered  Energy can be stored in different ways, and there are changes in the way it is stored when a system changes  The principle of conservation of energy states that: Energy cannot be created or destroyed, it can only be transferred from one store to another  This means that for a closed system, the total amount of energy is constant 
Efficiency of energy transfer  The efficiency of a system is a measure of how well energy is transferred in a system  Efficiency is defined as: The ratio of the useful power or energy transfer output from a system to its total power or energy transfer input  If a system has high efficiency, this means most of the energy transferred is useful  If a system has low efficiency, this means most of the energy transferred is wasted 
Pressure  Pressure is defined as The concentration of a force or the force per unit area  For example, when a drawing pin is pushed downwards:  It is pushed into the surface, rather than up towards the finger  This is because the sharp point is more concentrated (a small area) creating a larger pressure 
Liquid Pressure  A fluid is either a liquid or a gas When an object is immersed in a fluid, the fluid will exert pressure, squeezing the object  This pressure is exerted evenly across the whole surface of the fluid and in all directions  The pressure exerted on objects in fluids creates forces against surfaces  These forces act at 90 degrees (at right angles) to the surface The pressure of a fluid on an object creates a force normal (at right angles) to the surface  The pressure of a fluid on an object will increase with:  Depth within the fluid  Increased density of the fluid ### Calculating Pressure in Liquids  The pressure is more accurately the difference in pressure at different depths h in a liquid, since the pressure changes with the depth  The pressure due to a column of liquid can be calculated using the equation Δp = ρgΔh or in simple words —> $Rho Gravity Height$ 
Properties of Waves
 Waves transfer energy and information  Waves are described as oscillations or vibrations about a fixed point  For example, ripples cause particles of water to oscillate up and down  Sound waves cause particles of air to vibrate back and forth  In all cases, waves transfer energy without transferring matter  For water waves, this means it is the wave and not the water (the matter) itself that travels  For sound waves, this means it is the wave and not the air molecules (the matter) itself that travels  Objects floating on water provide evidence that waves only transfer energy and not matter 
Frequency  Frequency is defined as: The number of waves passing a point in a second  Frequency is given the symbol f and is measured in Hertz (Hz) 
Types of Waves  Transverse  e.g. vibrations of guitar string.  Longitudinal  e.g. Tsunami waves. 
Wave Speed  Wave speed is the speed at which energy is transferred through a medium  Wave speed is defined as: The distance travelled by a wave each second  Wave speed is given the symbol, ν, and is measured in metres per second (m/s), it can be calculated using: $wave speed = frequency × wavelength$ 
Features of a wave  When describing wave motion, there are several terms which are important to know, including:  Crest (Peak)  Trough  Amplitude  Wavelength  Frequency  Wave speed  Wavefront 
Wavefront  Wavefronts are a useful way of picturing waves from above: each wavefront is used to represent a single wave  The image below illustrates how wavefronts are visualised:  The arrow shows the direction the wave is moving and is sometimes called a ray  The space between each wavefront represents the wavelength  When the wavefronts are close together, this represents a wave with a short wavelength  When the wavefronts are far apart, this represents a wave with a long wavelength  Wave speed is defined as: The distance travelled by a wave each second  Wave speed is given the symbol ν and is measured in metres per second (m/s)  Wave speed is the speed at which energy is transferred through a medium  Transverse and longitudinal waves both obey the wave equation: V = f x lambda 
Crests & Troughs  A crest, or a peak, is defined as: The highest point on a wave above the equilibrium, or rest, position  A trough is defined as The lowest point on a wave below the equilibrium, or rest, position** 
 Where:  v = wave speed in metres per second (m/s)  f = frequency in Hertz (Hz)  λ = wavelength in metres (m) 
Amplitude  Amplitude is defined as: The distance from the undisturbed position to the peak or trough of a wave  It is given the symbol A and is measured in metres (m)  Amplitude is the maximum or minimum displacement from the undisturbed position 
Transverse Waves  Transverse waves are defined as: Waves where the points along its length vibrate at 90 degrees to the direction of energy transfer 
Wavelength  Wavelength is defined as: The distance from one point on the wave to the same point on the next wave  In a transverse wave:  The wavelength can be measured from one peak to the next peak  In a longitudinal wave  The wavelength can be measured from the centre of one compression to the centre of the next  The wavelength is given the symbol λ (lambda) and is measured in metres (m)  The distance along a wave is typically put on the xaxis of a wave diagram 
Longitudinal Waves  Longitudinal waves are defined as: Waves where the points along its length vibrate parallel to the direction of energy transfer 

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eiuhbogab, 22:14 10 Mar 23
good luck on ur gcses mate
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