physics

• Average speed


  The total distance travelled by an object divided by the total time taken

  
• Calculating average speed


  1. Total distance travelled

  2. Total time taken

  
• Calculating distance or time

  Using the formula: speed = distance / time

  
• Velocity


  A measure of the rate of change in position, described by both magnitude and direction

  
• Speed


  A measure of the rate at which distance is covered, described by magnitude only

  
• When there is no change in direction

  Velocity and speed are the same

  
• Position-time graphs


  • Show change in position over time, allow determination of speed and velocity

  
• Velocity-time graphs


  • Show change in velocity over time

  
• Stopwatches can be used to measure instantaneous speed
• Measuring speed with ticker timers


  Divide distance between dots by time interval (0.1s)

  
• Motion detectors


  • Emit ultrasound pulses, measure time for echoes to return to calculate distance and speed

  
• Speedometers


  • Measure wheel rotation speed to calculate vehicle speed, can be inaccurate

  
• GPS


  • Uses Doppler effect to calculate speed from changes in satellite radio wave frequency
• The use of GPS locators in the AFL
• The accuracy of speedometers is why some drivers get caught speeding even if they thought they were going the limit
• Older speedometer


  • Rotating magnet to help detect speed
• GPS


  Locating position accurately using signals from satellites
• How GPS measures speed

  1. Notices how radio waves from satellites change frequency as you move (Doppler effect)

  2. Calculates speed once per second

  
• Speed (or rate, r)


  Scalar quantity that measures the distance traveled (d) over the change in time (Δt), represented by the equation r = d/Δt

  
• Rate


  How a physical quantity changes with respect to time
• Acceleration


  Rate of change in velocity
• Displacement (Δx)


  Change in position of an object (i.e., Final position – Initial position)
• Velocity


  Measure of rate of change in position, with respect to time, described by a magnitude and direction

  
• Average speed


  Distance travelled divided by time taken v = D/t

  
• Acceleration


  How fast velocity changes over time, measured in m/s2

  
• Deceleration


  Acceleration in the opposite direction to velocity, resulting in a reduction of speed
• Force


  A push, pull or twist applied to one object by another, a vector quantity with magnitude and direction, measured in newtons (N)
• Weight


  The force of gravitational attraction on an object towards a planet, calculated as mass (m) times gravitational field strength (g)
• Mass


  Amount of matter in an object, measured in kilograms (kg), a scalar quantity
• Net force


  The combination of all forces acting on an object
• If the net force is zero, the forces are balanced. If one force is greater than the opposing force, the forces are unbalanced.
• Calculating diagonal force


  Use pythagoras Theorem to calculate the magnitude of the net force vector
• Newton's first law


  An object will stay in its state of motion or rest unless an external unbalanced force is applied
• The plane flies at a steady speed because no unbalanced net force is acting on it
• During bus maneuvers, an unbalanced force is needed to alter the vehicle's speed or direction
• Inertia


  An object's resistance to changes in motion, depends on its mass
• Newton's second law


  The acceleration of an object is equal to the total force on the object divided by its mass
• Newton's third law


  For every action there is an equal and opposite reaction
• Newton's third law involves two interacting objects experiencing equal but opposite forces
• Newton's Third Law of Motion

  For every action there is an equal and opposite reaction