P5

• Scalar quantity


  Has magnitude only
• Vector quantity


  Has magnitude and direction
• Examples of contact forces


  • Friction
  • Air resistance
  • Tension
  • Normal contact force
• Examples of non-contact forces


  • Gravitational force
  • Electrostatic force
  • Magnetic force
• Weight


  Force acting on an object due to gravity
• Weight and mass are directly proportional
• Resultant force


  Single force that has the same effect as all the original forces acting together
• Work done against friction causes a rise in temperature
• Elastic potential energy


  Energy stored in a stretched or compressed elastic object
• Moment of a force


  Turning effect of a force, M = F d
• Moment of a force

  The turning effect of a force
• Moment of a force

  Defined by the equation: moment of a force = force x distance
• If an object is balanced, the total clockwise moment about a pivot equals the total anticlockwise moment about that pivot
• Levers and gears


  • They can both be used to transmit the rotational effects of forces
• Pressure in a fluid

  The pressure at the surface of a fluid can be calculated using the equation: pressure = force normal to a surface / area of that surface
• Pressure due to a column of liquid


  Calculated using the equation: pressure = height of the column x density of the liquid x gravitational field strength
• A partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface, creating a resultant force upwards called the upthrust
• Atmospheric pressure


  The atmosphere is a thin layer of air round the Earth, and atmospheric pressure decreases with increasing altitude
• Distance


  How far an object moves, without involving direction
• 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
• Speed


  The rate of change of position, without involving direction
• Typical values for speed: walking ~1.5 m/s, running ~3 m/s, cycling ~6 m/s, speed of sound in air ~330 m/s
• Velocity


  The speed of an object in a given direction
• Acceleration


  The rate of change of velocity, calculated using the equation: acceleration = change in velocity / time taken
• Near the Earth's surface, any object falling freely under gravity has an acceleration of about 9.8 m/s^2
• Newton's First Law


  If the resultant force acting on an object is zero, a stationary object remains stationary and a moving object continues to move at the same velocity
• Newton's Second Law


  The acceleration of an object is proportional to the resultant force acting on it, and inversely proportional to the mass of the object, as described by the equation: resultant force = mass x acceleration
• Newton's Third Law


  Whenever two objects interact, the forces they exert on each other are equal and opposite
• The stopping distance of a vehicle is the sum of the thinking distance and the braking distance, and increases with speed
• Reaction time


  The time taken for a driver to respond to a hazard, typically 0.2-0.9 seconds, and can be affected by factors like tiredness, drugs, alcohol, and distractions
• Braking distance can be affected by adverse road conditions and poor vehicle condition
• Measure the effect of distractions on reaction time

  1. Evaluate the effect of various factors on thinking distance based on given data

  2. Measure the effect of distractions on reaction time
• Factors affecting braking distance


  • Adverse road conditions (wet or icy)
  • Poor condition of the vehicle's brakes or tyres
• Braking distance


  The distance required for road transport vehicles to come to rest in emergencies
• The greater the speed of a vehicle


  The greater the braking force needed to stop the vehicle in a certain distance
• The greater the braking force


  The greater the deceleration of the vehicle
• Dangers caused by large decelerations

  Brakes overheating and/or loss of control
• Momentum


  A property of moving objects, defined by the equation: momentum = mass x velocity
• In a closed system, the total momentum before an event is equal to the total momentum after the event
• Investigate collisions between laboratory trollies

  Using light gates, data loggers or ticker timers to measure and record data