Forces and Motion

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Cards (21)

  • Distance is how far an object moves
  • Distance does not involve direction so distance is a scalar quantity
  • Displacement includes both the distance and direction an object moves so displacement is a vector quantity
  • Speed does not involve direction so speed is a scalar quantity
  • The speed of a moving object is rarely constant
  • Typical values of transport
    • Walking - 1.5 m/s
    • Running - 3 m/s
    • Cycling - 6 m/s
    • Car - 25 m/s
    • Train - 55 m/s
    • Plane - 250 m/s
  • The speed of sound and the speed of the wind vary
  • A typical value for the speed of sound in air is 330 m/s
  • s=s =vt vt
    • Distance (s) in metres (m)
    • Speed (v) in metres per second (m/s)
    • Time (t) in seconds (s)
  • The velocity of an object is its speed in a given direction so velocity is a vector quantity
  • The speed of an object can be calculated from the gradient of its distance–time graph
  • If an object is accelerating, its speed at a particular time can be determined by drawing a tangent and measuring the gradient of the distance–time graph at that time
  • a=a =Δvt \frac{\Delta v}{t}
    • Acceleration (a) in metres per second squared (m/s2^2)
    • Change in velocity (∆v) in metres per second (m/s)
    • Time (t) in seconds (s)
  • An object that slows down is decelerating
  • The acceleration of an object can be calculated from the gradient of a velocity–time graph
  • The distance travelled by an object (or displacement of an object) can be calculated from the area under a velocity–time graph
  • Constant acceleration means uniform acceleration
  • v2−u2=v^2 - u^2 =2as 2as
    • Final velocity (v) in metres per second (m/s)
    • Initial velocity (u) in metres per second (m/s)
    • Acceleration (a) in metres per second squared (m/s2^2)
    • Distance (s) in metres (m)
  • Near the Earth’s surface any object falling freely under gravity has an acceleration of about 9.8 m/s2^2
  • An object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero as the friction force and accelerating force are the same and the object will move at its terminal velocity.
  • The terminal velocity is a fallings objects maximum speed