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Forces - Coggle Diagram
Forces
Weight, Mass and Gravity
Gravity
Force of attraction between masses
Effects of Gravity
Makes objects fall towards Earth
Gives objects weight
Mass
Amount of matter in an object
Measured in kilograms (kg)
Same everywhere
Weight
Force acting due to gravity
Measured in newtons (N)
Changes with gravitational field strength
Weight Equation
Weight = Mass × Gravitational Field Strength
W = mg
Gravitational Field Strength
Earth
9.8 N/kg
Moon
1.6 N/kg
Direct Proportion
Weight ∝ Mass
Centre of Mass
Point where mass appears concentrated
Contact and Non-Contact Forces
Forces
Push or pull
Measured in newtons (N)
Vector Quantities
Size and direction
Examples
Force
Velocity
Acceleration
Momentum
Scalar Quantities
Size only
Examples
Distance
Speed
Time
Mass
Temperature
Contact Forces
Objects touching
Examples
Friction
Air resistance
Water resistance
Tension
Normal contact force
Non-Contact Forces
Objects not touching
Examples
Gravitational force
Magnetic force
Electrostatic force
Interactions
Forces always occur in pairs
Equal and opposite forces
Act on different objects
Work Done
Work Done
Energy transferred by a force
Occurs when
Force moves an object
Equation
Work Done = Force × Distance
W = Fs
Units
Joule (J)
1 Joule
1 N force moves object 1 m
Examples
Lifting an object
Pushing an object
Pulling an object
Hooke's Law
Extension proportional to force
Equation
F = ke
F
Force (N)
k
Spring Constant (N/m)
e
Extension (m)
Spring Constant
Measure of stiffness
Resultant Forces
Free Body Diagrams
Show all forces acting on object
Forces shown as arrows
Arrow length represents magnitude
Arrow direction shows force direction
Resultant Force
Single force with same effect as all forces combined
Calculating Resultant Force
Same Direction
Add forces
Opposite Directions
Subtract forces
Units
Newtons (N)
Resultant Force = 0
Forces balanced
Object in equilibrium
Elastic Potential Energy
Stored when spring stretched
Stored when spring compressed
Equation
Ee = ½ke²
Depends on
Spring constant
Extension
Area Under Force-Extension Graph
Equals elastic potential energy stored
Equilibrium
Resultant Force = 0
Balanced Forces
Object
At rest
Or moving at constant velocity
On Scale Diagrams
Shape closes
Forms complete polygon
Resolving Forces
Used when force acts at an angle
Components
Horizontal Component
Vertical Component
Components at 90°
Combined effect equals original force
Elasticity
Stretching
Compressing
Bending
Transfers Energy
Scale Drawings
Used to calculate resultants
Method
Draw forces to scale
Join tip-to-tail
Draw resultant force
Measure length
Measure angle
Resultant Force
Magnitude
Direction
Energy Transfers
Moving Objects
Kinetic energy store
Lifting Objects
Gravitational potential energy store
Friction
Thermal energy store
Investigating Springs (Required Practical)
Apparatus
Spring
Clamp stand
Masses
Ruler
Method
Measure original length
Add mass
Measure extension
Repeat
Plot force-extension graph
Results
Straight line
Hooke's Law obeyed
Curved line
Limit of proportionality exceeded
Elastic Deformation
Object returns to original shape
When force removed
Inelastic Deformation
Object does not return to original shape
Permanent deformation
Limit of Proportionality
Force and extension no longer proportional
Graph stops being straight line