Force Density Pressure AS Physics 9702 Lecture 3
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W4 Forces, density and pressure
4.1 Turning effects of forces
Candidates should be able to:
1 understand that the weight of an object may be taken as acting at a single point known as its centre of gravity
2 define and apply the moment of a force
3 understand that a couple is a pair of forces that acts to produce rotation only
4 define and apply the torque of a couple
4.2 Equilibrium of forces
Candidates should be able to:
1 state and apply the principle of moments
2 understand that, when there is no resultant force and no resultant torque, a system is in equilibrium
3 use a vector triangle to represent coplanar forces in equilibrium
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Cambridge International AS & A Level Physics 9702 syllabus for 2025, 2026 and 2027. Subject content
4.3 Density and pressure
Candidates should be able to:
1 define and use density
2 define and use pressure
3 derive, from the definitions of pressure and density, the equation for hydrostatic pressure ∆p = ρg∆h
4 use the equation ∆p = ρg∆h
5 understand that the upthrust acting on an object in a fluid is due to a difference in hydrostatic pressure
6 calculate the upthrust acting on an object in a fluid using the equation F = ρgV (Archimedes’ principle)