Using physics to make things work

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  • Using physics to make things work
    • Moments
      • a moment is a turning force around a fixed point
      • Pivot- the point around which the moment acts
      • Load- the thing the moment is moving.
      • Effort- the force applied to move it
      • Affected by: increasing distance from pivot and increasing force
    • Balancing moments
      • Balance the force on each side of the pivot.
      • Calculate the moment so that the anti-clockwise and clockwise moments are equal.
      • Finding the mass of a beam
        • Calculate moment from force to pivot.
        • Work out where the centre of mass will be
        • Divide the moment by (centre of mass minus distance from pivot).
    • Pendulums
      • Pendulums oscillate.
      • Increasing the length of the pendulum increases the time period.
        • Time period is how long it takes for the pendulum to complete one oscillation.
      • Simple pendulum has: a mass (bob), and is suspended by string.
      • Amplitude is the angle between the equilibrium and the position of the bob.
    • Centripetal force
      • A force which acts in a circular motion towards the centre of the circle.
      • Not a force in it's own right as it is always caused by something else.
      • Objects moving in a circle are accelerating because their velocity is changing all of the time.
      • If the centripetal force stopped acting the object would continue moving at a tangent to the circle.
      • Increasing: mass of the object, and speed of the object increases centripetal force needed for movement.
      • Decreasing the radius of the circle increases the centripetal force needed.
    • Centre of mass
      • The point around which the mass of the object is thought to concentrate.
      • Depends on the shape of an object
      • A freely suspended object will come to rest with the centre of mass below the point of suspension.
    • Hydraulics
      • Uses the principle of pressure in liquids and that liquids can't be compressed.
      • Used to move heavy loads whilst exerting low force.
      • 1. Calculate the pressure on the slave piston using: pressure= force/ area.
      • 2. Calculate the force exerted from the master piston using the same equation- remember pressure stays the same!
    • Finding the centre of mass
      • 1. stick a pin through the shape and secure in a clamp stand.
      • 2. When it stops moving secure a plumb line from the same pin.
      • 3. Mark the position of the plumb line on the object.
      • 4. Repeat using a different point.
      • 5. Centre of mass is where the lines marking the plumb line are.
    • Pressure in liquids
      • Pressure increases with depth
      • Pressure is transmitted equally to all points in the liquid.

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