paper 2

• Force


  A push or a pull. The unit of force is the newton (N).
• Change of shape


  • Bending - Ends of object past each other
  • Stretching - Pulling ends apart
  • Compressing - Pushing ends together
• Deformation


  Changing shape and/or size as a result of forces being applied
• Elastic deformation


  Elastic materials return to their original shape and size after being stretched or squashed
• Inelastic deformation


  Inelastic materials do not return to their original shape and size after being stretched or squashed
• Elastic deformation


  • Rubber band stretched a little
• distance 


  how far an object moves
• speed


  rate of change of distance
• acceleration


  rate of change of velocity
• walking 


  1.5m/s
• running 


  3m/s
• cycling 


  6m/s
• car 


  13/30 m/s
• train


  50 m/s
• airplane 


  250 m/s
• weight 


  force acting on object due to gravity (non contact)
• gfs 


  objects with mass produce field
• 1st law


  object stays in same state of motion unless force acts upon it
• 2nd law


  F=ma
• 3rd law


  objects exert equal and opposite forces on each other
• • elastic deformation is reversed when the force is removed
• Work is done when a spring is extended or compressed.
• stopping distance = thinking distance + braking distance
• Stopping distances

  In an emergency, a driver must bring their vehicle to a stop in the shortest distance possible:
• reaction times


  -alcohol

  -drugs

  -tiredness
• braking distance

  • poor road and weather conditions, such as wet or icy roads
  • poor vehicle conditions, such as worn brakes or worn tyres
• Waves


  Vibrations that transfer energy from place to place without the transference of matter
• All waves will reflect and refract in the right circumstances
• Law of reflection


  Angle of incidence = angle of reflection
• Example of law of reflection


  • If a light ray hits a surface at 32°, it will be reflected at 32°
• Angle of incidence


  Angle between the normal and the incident ray
• Angle of reflection


  Angle between the reflected ray and the normal
• Normal


  Imaginary line at 90 degrees to the reflecting surface
• Specular reflection


  Reflection from a smooth, flat surface where light is reflected in a single direction
• Diffuse reflection


  Reflection from a rough surface where light is scattered in different directions
• Refraction


  The change in direction of a wave at the boundary between two materials with different densities
• Refraction of waves

  1. Wave changes speed

  2. Wave sometimes changes direction

  3. Upon entering a denser or less dense medium
• Density


  A measure of compactness and the ratio of mass to volume
• Density of a material

  Affects the speed that a wave will be transmitted through it
• In general, the denser the transparent material, the more slowly light travels through it