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Moments, Pressure & Upthrust - Coggle Diagram
Moments, Pressure & Upthrust
Moments
Turning Effect of a Force
Equation
Moment = Force × Distance
M = Fd
Units
Newton metre (Nm)
Distance
Perpendicular distance from pivot
To line of action of force
Increasing a Moment
Increase force
Increase distance from pivot
Balanced Object
Total Clockwise Moment
=
Total Anticlockwise Moment
Result
Object remains balanced
Levers
Simple Machines
Increase distance from pivot
Give larger moment
Less force needed
Examples
Spanner
Crowbar
Wheelbarrow
Bottle opener
Advantages
Multiply force
Reduce effort required
Gears
Circular discs with teeth
Functions
Transmit rotational effects
Transfer force
Change speed
Change direction of rotation
Gear Ratios
Large Gear Driving Small Gear
Small gear turns faster
Small Gear Driving Large Gear
Large gear turns slower
Larger turning force
Pressure
Definition
Force per unit area
Equation
Pressure = Force ÷ Area
p = F/A
Units
Pascals (Pa)
N/m²
Increasing Pressure
Increase force
Decrease area
Decreasing Pressure
Decrease force
Increase area
Examples
Sharp Knife
Small area
High pressure
Snow Shoes
Large area
Low pressure
Fluids
Liquids and Gases
Can flow
Exert pressure in all directions
Fluid Pressure
Caused by particles moving randomly
Acts in all directions
Acts at right angles to surfaces
Pressure in Liquids
Increases with depth
Increases with density
Equation
Pressure = Height × Density × Gravitational Field Strength
p = hρg
Variables
h
Depth (m)
ρ
Density (kg/m³)
g
Gravitational field strength (N/kg)
Upthrust
Force pushing upwards
Caused by pressure differences
Pressure greater at bottom than top
Result
Resultant upward force
Floating
Upthrust = Weight
Object floats
Sinking
Weight > Upthrust
Object sinks
Density and Floating
Less dense than fluid
Floats
More dense than fluid
Sinks
Submarines
Take in water
Sink
Remove water
Float
Atmospheric Pressure
Caused by air particles
Air has weight
Air particles collide with surfaces
Pressure acts in all directions
Altitude
Increase in altitude
Decrease in pressure
Reason
Fewer air particles above
Highest Pressure
Sea level
Lowest Pressure
High altitude
Key Equations
Moment = Force × Distance
M = Fd
Pressure = Force ÷ Area
p = F/A
Liquid Pressure = hρg
p = hρg
Exam Questions
Calculate moment
Calculate pressure
Explain how levers work
Explain gears
Explain why pressure increases with depth
Explain upthrust
Explain floating and sinking
Explain atmospheric pressure
Explain why atmospheric pressure decreases with altitude