T1: forces

• speed = distance / time
• acceleration = change in velocity / time
• distance traveled in a velocity-time graph is the area under the line
• final speed, initial speed, acceleration, distance?

  v" = u" +2as
• distance-time graphs = gradient is speed

  • flat = stationary
• velocity-time graph:

  • flat line = constant velocity
  • positive gradient = acceleration
  • negative gradient = deceleration
  • under graph = distance travelled
• acceleration from velocity-time graph:

  change in y / change in x = change in velocity / time
• forces act on a body to change the velocity, direction or both
• forces can change the shape of a body - stretching and squishing and twisting
• types of forces (8):

  • gravitational
  • electrostatic
  • weight
  • friction
  • thrust
  • up thrust
  • elastic potential
  • tension
• scalars = quantities with only magnitude
• vectors = quantities with both direction and magnitude
• scalar examples:

  • distance
  • speed
  • time
  • mass
• vector examples:

  • velocity
  • acceleration
  • force
  • weight
• force is a vector = both direction and magnitude
• resultant force is the overall force that acts on an object when two or more forces act on it
• newtons first law?

  if an object is at rest or in constant motion, it will stay that way until acted upon by exteral force
• newtons second law?

  if the resultant force is not zero, then an object will change speed or direction
• force = mass x acceleration
• friction is a force that opposes motion = acts in opposite direction
• weight = mass x gravitational field strength
• stopping distance = thinking distance + breaking distance
• thinking distance affected by:

  • tiredness
  • alcohol
  • speed of car
  • drugs
• breaking distance affected by:

  • road conditions
  • brake conditions
  • tyre conditions
  • speed of car
  • mass of car
• force acting on falling objects:

  • only force acting initially is weight = drag is proportional to velocity
  • object accelerates downwards
  • accelerates = velocity increases = drag increases = smaller resultant force = smaller acceleration
  • reaches a speed where drag = weight - no acceleration
  • this is terminal velocity
• force on springs:

  • length of spring without masses
  • hang mass = measure new length of spring
  • calculate extension of spring
  • increase weight
• hookes law: the spring extension is directly proportional to the force applied = straight line graph
• elastic behaviour is the ability of a material to return to its original shape after being stretched or compressed
• elastic limit = when a material is stretched beyond its elastic limit, it cannot return to its original shape