Forces and motion (3)

    Subdecks (2)

    Cards (27)

    • Instantaneous speed is the speed of the object at a specific point of time. You draw a tangent then calculate the gradient
    • The area under a velocity time graph is the displacement (from the area)
    • Deriving v= u + at
      a = Δv/ Δt = v-u/t
    • Deriving s=ut + 1/2at^2
      Displacement = area under graph so ut
      Displacement of triangle area 1/2 x (v-u) x t.
      (v-u) also = at so therefore when substituted in:
      s = ut + 1/2 at^2
    • deriving the equation s = 1/2 (u +v)t
      If you treat the area under the graph as a trapezium (u and v being the parallel sides and t is distance between them)
    • Deriving v^2 = u^2 +2as.
      T = (v-u) / a
      this can be substituted into s = 1/2 (u+v)t
      so s=1/2 (u+v) x (v-u)/a
      when rearranged (u+v)(v-u) = 2as
      v^2= u^2 + 2as.
    • To determine G:
      plot a displacement t^2 graph
      use Suvat equation s= ut + 1/2at^2. Since we know u= 0 we can cancel that out so s= 1/2gt^2 (as g = a)
    • Finding centre of gravity:
      Attach cork and pin onto the end of a clamp
      hole punch three holes into an irregular 2d shape
      put one of the holes through the pin and add a string with a mass weight on the end
      draw the cotton line’s direction
      see where they all cross over.
    • Moment = the turning effect of a force around an axis. Moment = force x perpendicular distance from the axis. Moment = fx
    • Principle of moments = the sum of the anti clockwise moments about a point is equal to the clockwise moments.
    • Couple = 2 forces being applied in parallel along different lines.
      a good example for this is a bike pedal
      The moment of a couple is known as a torque. Torque of a couple = one of the forces x perpendicular separation between forces.
    • Uncertanties:
      when adding or taking away simply add the uncertainties.
      when x or dividing, add the uncertainties.
      when There is a power, you times the uncertainty by the power.
    • Moment = force x perpendicular distance from the line of action of the point of rotation
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