kinematics

• Define displacement


  The distance travelled in a straight line in a particular direction from the start and end point
• Define instantaneous speed


  The speed of an object over a very short interval of time
• Define average speed


  The total distance travelled over the total time
• What is determined from the gradient of a displacement-time graph?

  velocity
• What does a straight line on a displacement-time graph show?


  constant velocity
• What does a curve on a displacement-time graph show?

  changing velocity i.e. acceleration
• What is determined from the gradient of a velocity-time graph?

  acceleration
• What is determined from the area under the curve on a velocity-time graph?

  displacement
• List four suvat equations.

  v=u+at, s=ut+1/2at2, s=1/2(u+v)t, v2-u2=2as
• Which quantity is constant in uniform motion?

  acceleration
• State the relationship between acceleration and resultant force

  acceleration is directly proportional to resultant force
• State the relationship between acceleration and mass

  accleration is inveresly proportional to mass
• Define braking distance


  the distance travelled under the braking force
• Define thinking distance


  the distance travelled during the reaction time
• Define stopping distance


  the sum of the thinking and braking distances
• State factors that can affect thinking distance

  fatigue, drugs, alcohol, distractions, speed
• State factors that can affect braking distance

  road condition, tyre condition, brake condition, speed
• Show that the relationship between speed and thinking distance is linear


  s = vt if t is constant then s α v
• Show that the relationship between speed and braking distance is s α v2

  Work done to slow down car is equal to the initial kinetic energy, W = Fs = 1/2mv2 , therefore s = (1/2mv2)/F if mass and braking force are constant then s α v2
• Explain why the horizontal velocity of a projectile is constant in projectile motion questions.

  Drag due to air resistance is assumed to be negligible and therefore there is no resultant force in the horizontal direction and hence no acceleration
• Explain why the vertical velocity of a projectile changes in flight.

  The weight of the projectile causes the projectile to accelerate downwards
• State Newton’s First Law of motion

  An object at constant velocity remains at constant velocity unless acted on by a resultant force