part 3

• scalar quantities have magnitude only
• vector quanities have size and direction
• straight diagonal line on distance time graph

  constant speed
• straight flat line on distance time graph

  stationary ( not moving )
• upwards curve on distance time graph 


  acceleration
• on a velocity time graph the gradient tell you the acceleration
• on a distance time graph the gradient tells you the speed
• straight diagonal line on velocity time graph

  constant acceleration
• straight flat line on velocity time graph

  constant velocity
• the area under the curve on a velocity time graph tells us

  distance traveled
• weight = mass x field strength
• the atmosphere is a thin layer of air around the earth
• the atmosphere gets less dense with increasing altitude
• air molecules colliding with a surface creates atmospheric pressure
• the weight of the air decreases the further above ground level we get
• as height increases there is always less air above a surface
• pressure = force / area
• stopping distance = thinking distance + breaking distance
• • thinking distance is the distance a vehicle travels in the time it takes for the driver to apply the brakes after realising they need to stop
• • braking distance is the distance a vehicle travels in the time after the driver has applied the brake

  Reaction times
• what affects reaction times

  tiredness drugs alcohol
• reaction time varies from 0.2 - 0.9s
• stopping distance is the total distance travelled from when the driver first sees obstacle to when it stops
• thinking distance is distance travelled by the car during drivers reaction time
• what is the stopping distance 


  the total distance traveled from when the driver first spots the obstruction to when the driver stops
• thinking plus braking equals stopping
• the greater the speed of the car the greater the stopping distance
• if you double the velocity of a car the kinetic energy quadruples
• the kinetic energy of the car is converted to thermal energy in the brakes
• large decelerations can cause brakes to overheat
• large decelerations can cause driver to lose control
• force = mass x acceleration
• weight = mass x field strength
• when a force causes an object to move through a distance work is done on the object
• a force does work when it causes displacement
• a force does work when it causes what ?


  displacement
• pressure = force / area
• perpendicular force exerts more pressure than a diagonal one because more of the force is directly hitting the surface
• free body diagrams shows the forces acting on an isolated object or system
• thinking distance is affected by


  speed of vehicle , reaction time