Physics Notes (IGCSE Edexcel)
Forces and Motion
Key Word: Definition:
Speed Distance travelled by object divided by time taken
Velocity Speed in a defined direction
Acceleration Change in velocity divided by time taken
Distance Measure of how far an object travels
Displacement Distance travelled in a defined direction
Distance-Time Graph Describes how an object’s distance changes over time
Distance (metres) = y-axis
Time (seconds) = x-axis
Gradient = Speed
Flat Line = Stationary object
Curved Line = Changing speed
Steeper Gradient = Increasing speed
Flatter Gradient = Decreasing speed
Constant Gradient = Constant Speed
Distance of 0 metres = Object returns to original position
Velocity-Time Graph Describes how an object’s velocity changes over time
Velocity (metres/second) = y-axis
Time (seconds) = x-axis
Gradient = Acceleration
Flat Line = Constant velocity
Curved Line = Changing acceleration
Uphill (/) = Acceleration
Downhill (\) = Deceleration
Velocity of 0 metres = Object at rest
Area Under Graph = Displacement
, Practical: Motion of Everyday Objects
Method:
. Mark same starting point on ramp using metre ruler
. Measure distance b/w light gates
. Use light gate to measure time for car w/o mass to roll down slope
. Repeat experiment at least 3 times for different masses added to car, remove anomalies and calculate average
. Speed = distance / time
. Experiment accuracy improvements:
Use light gates instead of stopwatch to avoid human errors from reaction time
Use pulley so car travels in straight line
,Key Word: Definition:
Force A push or a pull
(Forces on diagram act Can change speed, shape, direction or size of a body
in contact w/ object and
show magnitude of force)
Scalar Quantity with magnitude only
E.g.
Distance
Speed
Time
Energy
Mass
Vector Quantity with magnitude and direction
E.g.
Displacement
Velocity
Acceleration
Force
Momentum
Moment
Friction Force opposing motion when two surfaces are in direct contact
Results in heating
3 forms of friction:
Static friction/gripping, sliding friction, drag from fluids
Drag Frictional force opposing motion of objects in a fluid (liquid/gas)
/Air Resistance Drag reduced in fluids by more streamlined objects
Upthrust Upwards force exerted by fluid on an object floating in it
Weight Force due to gravity
Weight = mass x gravitational field strength
Tension Pull force exerted by each end of an object (e.g. - rope, string)
g Gravitational Field Strength (= 10N/Kg on earth)
Gravitational Force Force exerted between bodies due to their mass and the gravitational field strength
Electrostatic Force Non-contact force between two charged objects
Opposite charges attract but Like charges repel
Magnetic Force Non-contact force created by two magnets
Reaction Force Force opposing gravity that acts perpendicular to surface
Resultant Force Force = vector quantity (considers direction)
Resultant force when forces applied in opposite directions = Difference of forces
Resultant force when forces applied in same direction = Sum of forces
, Stopping Distance Distance travelled by car between first spotting the hazard and stopping
Stopping Distance = Thinking Distance + Braking Distance
Min/Max Stop Distance Smallest/Largest value given in a graph or table
Thinking Distance Distance car travels between realising need to brake and applying brakes
Thinking Distance = Reaction Time x Speed Travelling
Factors affecting Speed of Car
Thinking Distance Reaction Time
Intoxication
Tiredness
External Distractions
Braking Distance Distance car travels between applying brakes and coming to a stop
Requires Work/Kinetic Energy
Braking Distance = ½mv2 = Fxd
Factors affecting Speed of Car
Braking Distance Mass of Car
Road Conditions (Icy, Wet)
Car Conditions (Worn tires, Worn brake pads)
Terminal Velocity Maximum velocity an object can reach when falling through a fluid
Occurs when weight = air resistance
Increased weight → Increased speed
Increased surface area (hence use of parachute) → Increased air resistance
Increased speed → Increased air resistance
Freefaller:
1. Initially no air resistance, only weight
2. Freeflaller falls → rapidly accelerates
Because weight (downward force) > air resistance (upward force)
3. Increased speed → Increased air resistance
So acceleration (downwards resultant force) decreases
4. Terminal velocity eventually reached
Because weight = air resistance so not accelerating
5. Parachute deployed
Increased surface area → Increased air resistance
6. Freefaller decelerates
Because air resistance (upward force) > weight (downward force)
7. Freefaller reaches new terminal velocity
Because weight = air resistance
8. Freefaller lands
Measuring . Use stopwatch to measure time ball falls for in viscous liquid
Terminal Velocity . Use ruler to measure distance ball travels at different intervals (indicated by bands)
Practical Improvements:
. Calculate speed ball travels s for each distance (s = d/t)
. More viscous liquid → . Plot graph of velocity against time
slow down ball → easier to find speed
. Larger intervals b/w bands . At max velocity, graph plateaus and has gradient zero
. Taller tube → travels at TV longer
. Repeat experiment 5 times and take average for speed so more reliable
Forces and Motion
Key Word: Definition:
Speed Distance travelled by object divided by time taken
Velocity Speed in a defined direction
Acceleration Change in velocity divided by time taken
Distance Measure of how far an object travels
Displacement Distance travelled in a defined direction
Distance-Time Graph Describes how an object’s distance changes over time
Distance (metres) = y-axis
Time (seconds) = x-axis
Gradient = Speed
Flat Line = Stationary object
Curved Line = Changing speed
Steeper Gradient = Increasing speed
Flatter Gradient = Decreasing speed
Constant Gradient = Constant Speed
Distance of 0 metres = Object returns to original position
Velocity-Time Graph Describes how an object’s velocity changes over time
Velocity (metres/second) = y-axis
Time (seconds) = x-axis
Gradient = Acceleration
Flat Line = Constant velocity
Curved Line = Changing acceleration
Uphill (/) = Acceleration
Downhill (\) = Deceleration
Velocity of 0 metres = Object at rest
Area Under Graph = Displacement
, Practical: Motion of Everyday Objects
Method:
. Mark same starting point on ramp using metre ruler
. Measure distance b/w light gates
. Use light gate to measure time for car w/o mass to roll down slope
. Repeat experiment at least 3 times for different masses added to car, remove anomalies and calculate average
. Speed = distance / time
. Experiment accuracy improvements:
Use light gates instead of stopwatch to avoid human errors from reaction time
Use pulley so car travels in straight line
,Key Word: Definition:
Force A push or a pull
(Forces on diagram act Can change speed, shape, direction or size of a body
in contact w/ object and
show magnitude of force)
Scalar Quantity with magnitude only
E.g.
Distance
Speed
Time
Energy
Mass
Vector Quantity with magnitude and direction
E.g.
Displacement
Velocity
Acceleration
Force
Momentum
Moment
Friction Force opposing motion when two surfaces are in direct contact
Results in heating
3 forms of friction:
Static friction/gripping, sliding friction, drag from fluids
Drag Frictional force opposing motion of objects in a fluid (liquid/gas)
/Air Resistance Drag reduced in fluids by more streamlined objects
Upthrust Upwards force exerted by fluid on an object floating in it
Weight Force due to gravity
Weight = mass x gravitational field strength
Tension Pull force exerted by each end of an object (e.g. - rope, string)
g Gravitational Field Strength (= 10N/Kg on earth)
Gravitational Force Force exerted between bodies due to their mass and the gravitational field strength
Electrostatic Force Non-contact force between two charged objects
Opposite charges attract but Like charges repel
Magnetic Force Non-contact force created by two magnets
Reaction Force Force opposing gravity that acts perpendicular to surface
Resultant Force Force = vector quantity (considers direction)
Resultant force when forces applied in opposite directions = Difference of forces
Resultant force when forces applied in same direction = Sum of forces
, Stopping Distance Distance travelled by car between first spotting the hazard and stopping
Stopping Distance = Thinking Distance + Braking Distance
Min/Max Stop Distance Smallest/Largest value given in a graph or table
Thinking Distance Distance car travels between realising need to brake and applying brakes
Thinking Distance = Reaction Time x Speed Travelling
Factors affecting Speed of Car
Thinking Distance Reaction Time
Intoxication
Tiredness
External Distractions
Braking Distance Distance car travels between applying brakes and coming to a stop
Requires Work/Kinetic Energy
Braking Distance = ½mv2 = Fxd
Factors affecting Speed of Car
Braking Distance Mass of Car
Road Conditions (Icy, Wet)
Car Conditions (Worn tires, Worn brake pads)
Terminal Velocity Maximum velocity an object can reach when falling through a fluid
Occurs when weight = air resistance
Increased weight → Increased speed
Increased surface area (hence use of parachute) → Increased air resistance
Increased speed → Increased air resistance
Freefaller:
1. Initially no air resistance, only weight
2. Freeflaller falls → rapidly accelerates
Because weight (downward force) > air resistance (upward force)
3. Increased speed → Increased air resistance
So acceleration (downwards resultant force) decreases
4. Terminal velocity eventually reached
Because weight = air resistance so not accelerating
5. Parachute deployed
Increased surface area → Increased air resistance
6. Freefaller decelerates
Because air resistance (upward force) > weight (downward force)
7. Freefaller reaches new terminal velocity
Because weight = air resistance
8. Freefaller lands
Measuring . Use stopwatch to measure time ball falls for in viscous liquid
Terminal Velocity . Use ruler to measure distance ball travels at different intervals (indicated by bands)
Practical Improvements:
. Calculate speed ball travels s for each distance (s = d/t)
. More viscous liquid → . Plot graph of velocity against time
slow down ball → easier to find speed
. Larger intervals b/w bands . At max velocity, graph plateaus and has gradient zero
. Taller tube → travels at TV longer
. Repeat experiment 5 times and take average for speed so more reliable
