Forces, Density & Pressure + Work, Energy &
Power + Deformation of Solids
Table of Content
Forces, Density & Pressure................................................................................................................................... 1
Moments..................................................................................................................................................................... 1
Density & Pressure.................................................................................................................................. 2
Work, Energy & Power................................................................................................................................. 4
Terminology + Key Information....................................................................................................... 4
Deformation of Solids.................................................................................................................................. 5
Tensile & Compressive Forces........................................................................................................ 6
Calculating K from Hooke’s Law → Experiments..................................................................7
Series & Parallel Strings........................................................................................................................ 8
Other Terminology + Key Information........................................................................................ 9
Elastic & Plastic Deformation........................................................................................................... 11
Forces, Density & Pressure
Moments
Centre of Gravity: The point at which the weight of an object acts
→ An object is stable when its centre of gravity lies above its base
+ Wider base = lower centre of gravity and higher stability
+ Narrower base = higher centre of gravity and lower stability
Moment [Unit: Nm]: Turning effect of a force
, Moment of force = force x perpendicular distance of the pivot from the line of
action of the force
Anti-clockwise moment = clockwise moment → equilibrium/balanced
Couples - moments:
→ Pair of forces that are:
+ Equal in magnitude
+ Opposite directions
+ Perpendicular to the distance between them
+ Not in the same line of action - not acting on the same part of the object
Torque of couple: The total moment caused by a couple
+ Torque = Force x perpendicular distance [Ʈ = F x d]
Density & Pressure
Density: mass per unit volume
m
ρ=
V
→ Floating = less dense than the liquid
Pressure: Force acting normally (perpendicularly) per unit cross-sectional area
→ Scalar [ Nm−2 or Pa]
F
P= ∨P=ρ× g ×h
A
→ Second equation - Hydrostatic Pressure
Hydrostatic Pressure: Pressure exerted by a fluid at equilibrium (when amount,
volume, pressure, temperature, density,... of liquid is constant) at a given point
within fluid due to gravity
= Pressure in the fluid increases with depth
Δ P=ρ g Δ h
Derivation:
Weight of liquid
1. P=
Area
mg
2. P= → m=ρ V
A
Power + Deformation of Solids
Table of Content
Forces, Density & Pressure................................................................................................................................... 1
Moments..................................................................................................................................................................... 1
Density & Pressure.................................................................................................................................. 2
Work, Energy & Power................................................................................................................................. 4
Terminology + Key Information....................................................................................................... 4
Deformation of Solids.................................................................................................................................. 5
Tensile & Compressive Forces........................................................................................................ 6
Calculating K from Hooke’s Law → Experiments..................................................................7
Series & Parallel Strings........................................................................................................................ 8
Other Terminology + Key Information........................................................................................ 9
Elastic & Plastic Deformation........................................................................................................... 11
Forces, Density & Pressure
Moments
Centre of Gravity: The point at which the weight of an object acts
→ An object is stable when its centre of gravity lies above its base
+ Wider base = lower centre of gravity and higher stability
+ Narrower base = higher centre of gravity and lower stability
Moment [Unit: Nm]: Turning effect of a force
, Moment of force = force x perpendicular distance of the pivot from the line of
action of the force
Anti-clockwise moment = clockwise moment → equilibrium/balanced
Couples - moments:
→ Pair of forces that are:
+ Equal in magnitude
+ Opposite directions
+ Perpendicular to the distance between them
+ Not in the same line of action - not acting on the same part of the object
Torque of couple: The total moment caused by a couple
+ Torque = Force x perpendicular distance [Ʈ = F x d]
Density & Pressure
Density: mass per unit volume
m
ρ=
V
→ Floating = less dense than the liquid
Pressure: Force acting normally (perpendicularly) per unit cross-sectional area
→ Scalar [ Nm−2 or Pa]
F
P= ∨P=ρ× g ×h
A
→ Second equation - Hydrostatic Pressure
Hydrostatic Pressure: Pressure exerted by a fluid at equilibrium (when amount,
volume, pressure, temperature, density,... of liquid is constant) at a given point
within fluid due to gravity
= Pressure in the fluid increases with depth
Δ P=ρ g Δ h
Derivation:
Weight of liquid
1. P=
Area
mg
2. P= → m=ρ V
A
