Physics 6.1

• Speed


  The measure of how fast something is travelling. The distance travelled in a certain amount of time. Measured in m/s or km/h.
• Speed equation


  Speed = Distance / Time
• A car travels 24 metres in 2 seconds, the speed is 12 m/s
• Velocity


  The difference to speed is that velocity has a direction as well as distance. Displacement is the distance moved in a straight line, or a given direction from a starting point.
• Velocity equation


  Velocity = Displacement / Time
• A car travels 24m east in 3s, the velocity is 8m/s east
• Scalar


  A measurement that has size only
• Vector


  A measurement that has size and direction
• Distance/Time Graph


  • The steeper the line, the faster the distance is travelled in the time
  • Stationary = No movement
  • Use the equation to find the speed at a point or the area for the average speed
• Speed/Time Graph


  • Constant Speed
  • Consistent Deceleration
  • To calculate the total distance, find the area under the graph
• Acceleration equation


  Acceleration = Change in velocity / Time taken
• Acceleration


  • If an object is speeding up, acceleration is positive
  • If an object is slowing down, acceleration is negative
  • Deceleration is already negative, no need for negative sign
• Acceleration of 10 m/s² or greater is the acceleration of falling from a high place or a collision between cars
• Stopping Distance


  • Consists of thinking distance and braking distance
  • The faster the vehicle is moving, the greater the thinking and braking distance will be
• Thinking Distance


  The distance a vehicle will travel in the time it takes the driver to react
• Things that would increase thinking distance

  • Drinking alcohol
  • Being distracted by things around you
  • Speeding
  • Tiredness
  • Poor visibility
  • Taking drugs
• Braking Distance


  The distance a vehicle will travel after its brakes have been applied
• Things that would increase braking distance

  • Greater weight of the car
  • Faulty brakes
  • Worn tyres
  • Wet/icy/oil covered roads
  • Speed
• At 30 mph, the thinking distance doubles and the braking distance quadruples compared to 60 mph