speed-time graphs and acceleration

• • Speed is the distance a vehicle travels each second.
  • The units for speed are m|s
  • When a car increases its speed, we say that it is accelerating.
  • A car that gets slower each second is said to be decelerating or to have a negative acceleration.
  • The units of acceleration are m/s^2
• • speed = distance travelled/time taken regardless of direction
  • velocity is speed in a given direction
• • Scalar quantities have magnitude only.
  • Vector quantities have magnitude and an associated direction.
  • A vector quantity may be represented by an arrow. The length of the arrow represents the magnitude, and the direction of the arrow the direction of the vector quantity.
• Distance is how far an object moves
• Distance does not involve direction
• Distance is a scalar quantity
• Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point, and the direction of that straight line
• Displacement is a vector quantity
• Speed does not involve direction
• Speed is a scalar quantity
• Factors affecting the speed at which a person can walk, run, or cycle include: age, terrain, fitness, and distance travelled
• Walking speed is approximately 1.5 m/s
• Running speed is approximately 3 m/s
• Cycling speed is approximately 6 m/s
• For an object moving at constant speed, the distance travelled in a specific time can be calculated using the equation: s = v * t
• Distance, s, is in metres (m)
• Speed, v, is in metres per second (m/s)
• Time, t, is in seconds (s)
• The velocity of an object is its speed in a given direction
• Velocity is a vector quantity
• Motion in a circle involves constant speed but changing velocity
• If an object moves along a straight line, the distance travelled can be represented by a distance-time graph
• The speed of an object travelling in a straight line can be calculated from the gradient of its distance-time graph
• If an object is accelerating, its speed at any particular time can be determined by drawing a tangent and measuring the gradient of the distance-time graph at that time.
• What is the word equation for acceleration

  acceleration=change in velocity/time taken
• • The acceleration of an object can be calculated from the gradient of a velocity-time graph. (HT only)
  • the distance travelled by an object (or displacement of an object) can be calculated from the area under a velocity-time graph.
  • The area under a velocity-time graph determines distance travelled (or displacement)
• letter for distance

  s
• letter for speed

  v
• Equation for distance traveled

  s=vt
• Word equation for final velocity in terms of acceleration

  final velocity= initial velocity + (acceleration*time)
• Word equation for distance in terms of acceleration

  distance=1/2(initial velocity+final velocity)*time