# GCSE Physics

 Formula for Density: Density = Mass / Volume Density is measured in g/cm cubed or kg/m cubedMass is measured in g or kgVolume is measured in cm cubed or m cubed Formula for Pressure: Pressure = Force / Area Pressure is measured in PascalsForce is measured in NewtonsArea is measured in m squared Equation for Pressure Difference Pressure difference = height x density x gravity Pressure difference is measured in PascalsHeight is measured in cm or mDensity is measured in g/cm cubed or kg/m cubedGravity is 10 The States of Matter Solids = particles are arranged in a regular way close together. Can vibrate about a fixed position. They have a fixed shape. Liquid = Particles are still together. Can move between and past each other, in a random jostling manner. Some are touching. They flow to take the shape the container they are in. Gas = Particles are much, much further apart. They move more rapidly than in liquids. Random motion of the particles. Gases expand to fill the container they are in. Definition of air pressure or how do air/gas particles cause pressure? The gas particles collide with the container walls exerting a force. Pressure is the force per unit area. Absolute zero and the Kelvin scale Absolute zero is the lowest temperature that can be theoretically reached. There can be no lower temperature as the particles cannot do less than not move at all. To convert degrees Celsius to degrees Kelvin we add 273. To convert degrees Kelvin to degrees Celsius we subtract 273. Law of Pressure Write the equation: P1 / T1 = P2 / T2 Rearrange the equation : T2 x P1/T1 = P2 Pressure and Volume Write out the equation: P1V1 = P2V2 Rearrange the equation: P1V1/P2 = V2 Remember this is at constant temperature and fixed mass Average Speed Average speed is measured in meters per second. Average speed is calculated by dividing the total distance travelled by the total time taken. Average speed = distance/time Distance/Time Graphs On a distance time graph a straight line indicates constant speed. A flat line means the object has stopped. A smooth curve shows a steady increase in speed. Acceleration If an object is increasing in speed as it travels we say that it is accelerating. If it decreases its speed we say that it is decelerating. Acceleration = change in velocity / time taken A = (v- u) t A = accelerationv = final velocityu = inicial velocityt = time in seconds Scalar and Vector Quantities Force is a vector quantity as is velocity, acceleration and weight. They all have direction as well as size with a unit. Speed, temperature and mass are scalar quantities; these only have a size not a direction. To fully describe a force you have to state the size and direction. Friction Friction is a force that slows/stops motion between touching surfaces. Friction reduces with speed. It acts against the direction of movement. Air resistance of an accelerating object increases until it balances the driving force and the object stops accelerating. Friction converts kinetic energy to heat energy. It also causes wear on the surfaces which are in contact. This can be reduced by lubrication. Mass and Force Force = Mass x Acceleration AuthorCoryandmitzy ID115711 Card SetGCSE Physics DescriptionGCSE physics revision Updated2011-11-09T19:02:29Z Show Answers