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4. Forces, density and pressure

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  1. 4.1 Turning effects of forces

    1. 4.1.1The weight of an object may be taken as acting at a single point known as

      • understand that the weight of an object may be taken as acting at a single point known as its centre of gravity

    2. 4.1.2The moment of a force

      • define and apply the moment of a force

    3. 4.1.3A couple is a pair of forces that acts to produce rotation only

      • understand that a couple is a pair of forces that acts to produce rotation only

    4. 4.1.4The torque of a couple

      • define and apply the torque of a couple

  2. 4.2 Equilibrium of forces

    1. 4.2.1The principle of moments

      • state and apply the principle of moments

    2. 4.2.2That, when there is no resultant force and no resultant torque, a system is

      • understand that, when there is no resultant force and no resultant torque, a system is in equilibrium

    3. 4.2.3A vector triangle to represent coplanar forces in equilibrium

      • use a vector triangle to represent coplanar forces in equilibrium

  3. 4.3 Density and pressure

    1. 4.3.1Density

      • define and use density

    2. 4.3.2Pressure

      • define and use pressure

    3. 4.3.3Derive, from the definitions of pressure and density, the equation

      • derive, from the definitions of pressure and density, the equation for hydrostatic pressure ∆p = ρg∆h

    4. 4.3.4The equation ∆p = ρg∆h

      • use the equation ∆p = ρg∆h

    5. 4.3.5The upthrust acting on an object in a fluid is due to a difference in

      • understand that the upthrust acting on an object in a fluid is due to a difference in hydrostatic pressure

    6. 4.3.6The upthrust acting on an object in a fluid using the equation F = ρgV

      • calculate the upthrust acting on an object in a fluid using the equation F = ρgV (Archimedes’ principle)