Physics IGCSE Revision Notes
Physics Unit 1 Revision (Forces and Motion)
Movement and Position:
Distance Time Graphs:
- Straight Line: Stationary:
- Diagonal Upwards Line: Object is moving at a steady speed (forwards)
- Diagonal Downwards Line: Object is moving backwards
- Up Curve: Acceleration
- Down Curve: Deceleration
- Speed is Gradient
Average Speed Equation:
- Average Speed = Distance Moved / Time Taken
Motion Practical:
- Put a toy car on a table with a pulley at the end of the table.
- The toy car and slotted masses should be attached to the pulley with a string
- The toy car and pulley are kept apart with a metre ruler.
- A metre ruler is used because it has a bigger scale and can be read easily compared to millimetre. This
improves precision of the experiment.
- To improve accuracy, metre ruler should be kept straight with a set square.
- Time stop watch as the car moves.
- Ensure that the readings are read at eye level to avoid parallax error.
- Repeat the experiment with different distances (0.2m, 0.4m, 0.6m)
- Repeat each distance at least three times to obtain 3 sets of timings.
- Get an average of the time and plot a graph.
- S=D/T
Acceleration Equation:
- Acceleration = Change in Velocity / Time Taken
Velocity Time Graphs:
- Horizontal Line line: Constant Speed
- Upwards Diagonal Line: Constant Acceleration
- Downwards Diagonal Line: Constant Deceleration
- Distance Moved: Area under the graph
- Acceleration: Gradient of Line
Forces, Movement, Shape and Momentum:
Effects of Forces:
- Speed: Can allow objects to speed up, slow down or be stationary
- Shape: Affect momentum
- Direction: Can change dependent on resultant forces
Types of Forces:
- Upthrust (Buoyancy)
- Lift
- Thrust (Push)
- Weight (Gravitational force acting on an object)
- Friction (Opposes Motion)
- Drag (Resistance with particles colliding)
- Magnetic (Magnetic Attraction)
- Electrostatic (Changes in charge)
Scalar and Vector Quantities:
- Scalar: Only show magnitude (Eg. distance, speed, energy, mass)
- Vector: Show both magnitude and direction (Eg. displacement, velocity, force weight)
,Resultant Forces:
- Add up in the same direction
- Subtract in opposite direction
Force Equation:
- Force = Mass * Acceleration
Weight Equation:
- Weight = Mass * Gravitational Field Strength
- GFS is 10N/kg
Stopping Distances:
- Stopping Distance = Thinking Distance + Braking Distance
- Thinking Distance: Distance travelled in the time it takes driver to react
- Braking Distance: Distance travelled by car whilst braking
Factors Affecting Stopping Distances:
Thinking Distance Braking Distance
- Reaction Time - Speed
- Tiredness - Quality of brakes (maintained regularly)
- Drugs - Quality of tyres (min depth of 1.6mm in order
- Alcohol to rid of water in wet conditions)
- Phones - How good the grip on the surface is (weather
- Annoying Passengers conditions and terrain (eg. tarmac))
- Stress
- Diseases
- Eating and Drinking
- Speed
Terminal Velocity:
- Terminal velocity is the max constant velocity an object reaches falling
- When someone jumps out of a plane, their weight forces is much larger than their drag force and the
resultant force accelerates downwards.
- As the jumper’s velocity increases, the drag force increases and the resultant force gets lower.
- Once the forces are balanced, the person reaches terminal velocity at a constant speed and he stops
accelerating and there is no resultant force.
Extension Springs Practical:
- Attach a rubber band to a newton meter
- Measure the length of the object
- Add a 10g weight on the end of the meter and measure the length
- Continue to add on weights
- Plot the graph
Hooke’s Law:
- The force acting on a spring is directly proportional to its extension
- Force = constant * extension
, Elastic Behaviour:
- The ability for a material to recover its original shape after the forces causing deformation have been
removed
Momentum and Safety Features:
- Momentum can be used to explain safety features. For example an airbag in the car:
- With an airbag, the change in momentum takes place over a longer period of time so less force is exerted
on the passenger, reducing the risk of death. Furthermore, the velocity decreases over a longer period of
time with the same momentum, further reducing the force and risk of death
Conservation of Momentum:
- Momentum is always conserved
- Momentum before collision = momentum after collision
Change in Momentum Equation:
- Change in Momentum (kg m/s) = Force (N) * Time (s)
Moment Equation:
- Moment = force * perpendicular distance from pivot
Centre of Gravity:
- An objects centre of gravity is where all of its weight acts through
- To Find the centre of gravity for irregular shaped objects:
- Irregular shape is suspended from a pivot and allowed to settle
- Plumb line held next to pivot and draw vertical line from pivot
- Repeat, suspending at different points
- Centre of gravity located at intersection of lines
Principle of Moments:
- Clockwise Moment = Anti Clockwise Moment
Physics Unit 2 Revision (Electricity)
Mains Electricity:
Protecting Devices:
- Insulation: Casing an appliance with an insulator that doesn’t conduct heat, eg, rubber
- Double Insulation: Casing the appliance in plastic twice so that the user can’t touch any electric parts and
there is no need for an earth wire
- Earthing: If the live wire touches the casing (sometimes metal) the earth wire makes a safe path for the
current to flow into the ground
- Fuses: Fuses are put in the circuit and have a low melting point as they heat up and melt if the current gets
too high so it breaks the circuit. The rating is normally higher than the appliance current (eg, 3A). They
need to be replaced.
- Circuit Breakers: If a larger current flows, the electromagnet will pull and separate the contacts and will
break the circuit. But it has to be reset and it is faster and more reliable than fuses
Resistors, Energy and Temperature in Home Devices:
- As the resistors slow down the electrons, the kinetic energy is transferred to heat energy which increases
the temperature. This is used in hair dryers
Power Equation:
- Power = Current * Voltage
- P=I*V
- Watts (W) = Amps (A) * Volts (V)
Energy Transferred Equation:
- Energy Transferred = Current * Voltage * Time
- E=I*V*t
- Joules (J) = Amps (A) * Volts (V) * seconds (s)
- 1 Kiloamp = 1000A
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