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CAIE
4. Forces, density and pressure
4.1 Turning effects of forces
- understand that the weight of an object may be taken as acting at a single point known as its centre of gravity
- define and apply the moment of a force
- understand that a couple is a pair of forces that acts to produce rotation only
- Use the concedefine and apply the torque of a couplept of efficiency to solve problems
4.2 Equilibrium of forces
- state and apply the principle of moments
- understand that, when there is no resultant force and no resultant torque, a system is in equilibrium
- use a vector triangle to represent coplanar forces in equilibrium
4.3 Density and pressure
- define and use density
- define and use pressure
- derive, from the definitions of pressure and density, the equation for hydrostatic pressure ∆p = ρg∆h
- use the equation ∆p = ρg∆h
- understand that the upthrust acting on an object in a fluid is due to a difference in hydrostatic pressure
- calculate the upthrust acting on an object in a fluid using the equation F = ρgV (Archimedes’ principle)