Physics

• Speed

  How fast you're going, with no regard to direction
• Velocity


  How fast you're going, with direction specified
• An object can have constant speed with changing velocity


  This happens when the object is changing direction while traveling at the same speed
• Calculating average speed


  Distance moved / Time taken
• Acceleration


  How quickly velocity is changing
• Acceleration is not the same as velocity or speed
• Acceleration can be a change in speed or a change in direction, or both
• Acceleration formula


  Acceleration = Change in Velocity / Time taken
• Calculating final velocity


  v^2 = u^2 + 2as
• You might not be told what equation to use in the exam, so make sure you can spot when to use each equation
• Calculating average speed from distance and time

  Average speed = Distance / Time
• Calculating acceleration from initial and final velocities, and time

  Acceleration = (Final velocity - Initial velocity) / Time
• Distance-time graph


  Tells you how far something has travelled
• Distance-time graph


  • Gradient (slope) gives the speed of the object
  • Flat sections represent constant speed
  • Uphill sections represent acceleration
  • Downhill sections represent deceleration
• Velocity-time graph


  Shows how an object's velocity changes over time
• Velocity-time graph


  • Gradient represents acceleration or deceleration
  • Flat sections represent constant speed
  • Uphill sections represent acceleration
  • Downhill sections represent deceleration
  • Area under the graph represents distance travelled
• Gravity is the force of attraction between all masses
• Effects of gravity


  • It makes all things near a planet or other large mass accelerate towards the centre of that mass
  • It gives everything near a planet or other large mass weight
  • It keeps planets and moons in their orbits
• Mass


  The amount of material in an object
• Weight


  The force of gravity pulling an object towards the centre of a planet or other large mass
• An object has the same mass whether it's on Earth or on the Moon, but its weight will be different</b>
• Weight formula

  Weight = Mass x Gravitational field strength
• Weight is a force due to gravity and it changes depending on the strength of the gravitational field the object is in
• Types of force


  • Reaction force
  • Electrostatic force
  • Drag/air resistance/friction
  • Tension
• An object with a weight feels forces acting on it
• Fluid friction


  The force that opposes the motion of an object moving through a fluid (liquid or gas)
• Friction

  • Always acts to slow things down
  • Can be between solid surfaces gripping each other
  • Can be between solid surfaces sliding past each other
  • Can be fluid resistance or "drag"
• The most important factor in reducing fluid friction is keeping the shape of the object streamlined
• Bumps on cars can increase drag and slow them down
• Did (r, water ets) it fa dhe sasite destico to is water
• Friction is Always There to Slow things Down
• If an object hes for pregelg it along


  It will always se da (unless you're cut in space where there's son) Friction a
• Types of friction

  • Friction Betress Solid Surfaces Which Are Gripping
  • Friction Batween Solid Surfaces Which Are Sinding Past Each Other
  • Resistance or "drag" from fluids (liquids or gases, eg. air)
• The most important factor by finding high fudy is keeping the shape of the object streamed, New sports cars or boet hulls. Lomies and carevara heve "festas" on them to make them more streamlined and reduce drag
• Bashes on care pol their streamired shape

  Slow them down
• For given thrust

  The higher the drag the ar fhe tapeed of the car
• FRICTION ALWAYS INCREASED AS THE SPEED INCREASED-see page 9
• Resultant Force

  The overall force acting on an object
• Resultant Force = Mass x Acceleration
• Resultant Force

  • The bigger the force, the gate the accelaration or deceleration
  • The bigger the mess, the der the acceleration
  • To get big mess to accelerate as fast as a mess it needs a bigger force