Distance, speed & acceleration (2.1)

• Forces can change the position, motion and shape of an object
• Forces can make objects speed up, slow down and change direction
• What is a scalar quantity?

  Has only a size/ number. It cannot be negative
• What are some examples of a scalar quantity?

  Mass, speed, volume
• What is a vector quantity?

  A measurement having size and direction
• What are examples of a vector quantity?

  Velocity, force, acceleration
• The difference between velocity and speed is that velocity has direction
• Acceleration can be positive or negative
• The gradient of a velocity-time graph represents acceleration
• A horizontal line on a graph means that the object is travelling at constant speed unless it rungs along the x axis
• A straight line with a constant gradient which isn't horizontal tells us that the object has a constant rate of acceleration
• What do velocity-time graphs show?

  Velocity/ speed of a moving object which changes with time
• What is a stopping distance?

  The total distance needed by a car to stop
• What is a thinking distance?

  Distance travelled between reacting to a danger or a reason to stop the vehicle and breaking
• What is a braking distance?

  Distance travelled while braking
• How is stopping distance calculated?

  Thinking distance + braking distance
• What factors affect thinking distance?

  Influence of alcohol and drugs, tiredness, age
• What factors affect braking distance?

  Condition of tires, the road and brakes
• How is thinking distance calculated?

  Distance divided by time
• What is a reaction time?

  Time taken between seeing an event and reacting to it
• What are the advantages and disadvantages of humps in the road?

  Prevents damage to car and forces you to travel at a slower speed
• What are the advantages and disadvantages of road width restrictions?

  Helps cars to reduce their speeds and can cause excess traffic
• What are the advantages and disadvantages of fixed speed cameras?

  Helps drivers to slow down for that area of the road and drivers that know there are cameras will only slow down for that part of the road
• What are the advantages and disadvantages of mobile speed cameras?

  Encourages drivers to follow the speed limit and drivers may only slow down for that part of the road
• What safety features are in cars?

  Air bags, crumple zones, and safety belts
• What is a crumple zone?

  An area at the front of the car which is designed to collapse to prolong impact time in a crash