Science

• Motion and forces


  • Describing motion
  • Forces
  • Pressure in fluids
  • Balanced forces
  • Forces and motion
• Describing motion


  • Speed and the quantitative relationship between average speed, distance and time
  • Representation of a journey on a distance-time graph
  • Relative motion: trains and cars passing one another
• Forces


  • Pushes or pulls, arising from the interaction between 2 objects
  • Using force arrows in diagrams, adding forces in 1 dimension, balanced and unbalanced forces
  • Moment as the turning effect of a force
  • Forces associated with deforming objects; stretching and squashing-springs; with rubbing and friction between surfaces, with pushing things out of the way; resistance to motion of air and water
  • Forces measured in newtons, measurements of stretch or compression as force is changed
  • Force-extension linear relation; Hooke's Law as a special case
  • Work done and energy changes on deformation
  • Non-contact forces: gravity forces acting at a distance on Earth and in space, forces between magnets, and forces due to static electricity
• Pressure in fluids


  • Atmospheric pressure, decreases with increase of height as weight of air above decreases with height
  • Pressure in liquids, increasing with depth; upthrust effects, floating and sinking
  • Pressure measured by ratio of force over area-acting normal to any surface
• Balanced forces


  • Opposing forces and equilibrium: weight held by stretched spring or supported on a compressed surface
• Forces and motion


  • Forces being needed to cause objects to stop or start moving, or to change their speed or direction of motion (qualitative only)
  • Change depending on direction of force and its size
• Equilibrium


  State of an object when opposing forces are balanced
• Deformation


  Changing shape due to a force
• Linear relationship


  When two variables are graphed and show a straight line which goes through the origin, and they can be called directly proportional
• Newton


  Unit for measuring forces (N)
• Resultant force


  Single force which can replace all the forces acting on an object and have the same effect
• Friction


  Force opposing motion which is caused by the interaction of surfaces moving over one another. It is called 'drag' if one is a fluid
• Tension


  Force extending or pulling apart
• Compression


  Force squashing or pushing together
• Contact force


  One that acts by direct contact
• Fluid


  A substance with no fixed shape, a gas or a liquid
• Pressure


  The ratio of force to surface area, in N/ m2, and how it causes stresses in solids
• Upthrust


  The upward force that a liquid or gas exerts on a body floating in it
• Atmospheric pressure


  The pressure caused by the weight of the air above a surface