SP1 Motion

SP1a Vectors and Scalars

  • All forces have both a magnitude (size) and a direction, and are measured in newtons (N). 
  • Vector quantities - quantites that have size and direction. Forces are vectors. 
  • Scalar quantites - quantities that only have size, examples include distance, speed, energy and time.
  • Displacement is the distance covered in a straight line
  • The speed - how far an object moves in a certain time
  • Velocityspeed in a particular direction.
  • Acceleration - a measure of how fast velocity is changing.
  • Momentum - a combination of mass and velocity.  
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SP1b Distance/Time Graphs

  • Speed (m/s) = distance (m) ÷ time (s)
  • Calculated usng light gates - more accurate.
  • Adverage speeds for: walking - 1.4m/s, cycling - 6 m/s and train - 55m/s.
  • WInd - 5-20m/s and sound in air - 340m/s

Distance/Time Graph: 

  • Horizontal lines: object stationary 
  • Straight lines: constant speed 
  • Steep lines: faster constant speed
  • Curves: acceleration
  • Gradient: the speed of the object
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SP1c Acceleration

  • Acceleration - change in velocity , units are m/s ² and is a vector quantity.
  • accleration (m/s²)= change in velocity (m/s) ÷ time (s)
  • a = (v - u) ÷ t (v - final velocity, u - intial veloctiy)
  • (final velocity)² - (initial velocity)² = 2 x acceleration x distance 
  • v²-u²= 2ax
  • If there are no forces acting on a object in free fall, the acceleration due to gravity is 9.8m/s² or 10m/s².
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SP1d Velocity/Time Graphs

On a velocity/time graph:

  • horizontal lines: constant velocity 
  • sloping lines: accelerating (steeper the line, greater the acceleration)
  • line below horizontal axis: negative velocity (object moves opposite direction)
  • area under a velocity/time graph: distance travelled (distance= velocity x time/ base x height)
  • if the object is accelerating (sloping line), split the shape into a triange (area = 0.5 x b x h) and rectangle and find their areas separately. 
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