Speed, Distance, Time, and Acceleration

Speed, Distance, and Time Formulas

• Distance = Speed x Time.
• Speed = Distance / Time.
• Time = Distance / Speed.
• It's important to write out the full equation to get the mark; formula triangles don't count.

Calculating Speed from a Distance-Time Graph

• To find speed at a point on a distance-time graph:
• Read the distance traveled from the y-axis.
• Read the time from the x-axis.
• Divide the distance by the time to calculate the speed.
• Stationary portions on a distance-time graph are flat lines.

Acceleration on a Velocity-Time Graph

• Acceleration = (Final Speed - Initial Speed) / Time.
• Units for acceleration are meters per second squared (m/s²​​).
• Distance traveled is calculated by finding the area under the velocity-time graph.
• Split complex areas into triangles and rectangles for easier calculation.

Applying SUVAT Equations

• Equation for motion: V² = U² + 2as
• V = final velocity
• U = initial velocity
• a = acceleration
• s = distance
• Remember to consider deceleration as a negative acceleration.

Interpreting Motion Graphs

• Constant velocity is represented by a horizontal line on a velocity-time graph.
• Average velocity = Distance / Time.

Weight vs Mass

• Weight is measured in Newtons (N), and mass is measured in kilograms (kg).
• Mass remains constant regardless of location.
• Weight changes with gravity changes.
• Weight = Mass x Gravitational Field Strength (g).
• On Earth, weight = mass x ~10.
• On the Moon, weight = mass x ~1.6.

Types of Forces

• Forces can change an object's speed, direction, or shape.
• Contact forces require physical touching.
• Non-contact forces do not require touching.
• Examples: Magnetic force, electrostatic forces, and gravitational force.

Important Forces

• Normal Reaction Force: Perpendicular force exerted by a surface on an object.
• Friction: Opposes the motion between two sliding objects.
• Air Resistance: Drag force experienced when moving through the air.
• Upthrust: Upward force exerted by a fluid on an object (e.g., boat on water).
• Nuclear Force: Holds the nucleus of atoms together.

Balanced vs Unbalanced Forces

• Balanced forces result in no change in motion (stationary or constant speed).
• Unbalanced forces cause acceleration.

Forces on a Car

• Driving force from the engine propels the car forward.
• Air resistance opposes the car's motion.
• Friction between tires and the road can both oppose and enable motion.
• Weight acts downwards due to gravity.
• Normal reaction force acts upwards from the road.

Terminal Velocity

• Occurs when the force of air resistance equals weight.
• At terminal velocity, an object falls at a constant speed.
• Opening a parachute increases air resistance, reducing terminal velocity.

Relationship Between Force, Mass, and Acceleration

• Force = Mass x Acceleration.

Hooke's Law

• Force (or Weight) is proportional to extension until the elastic limit is reached.
• Remember the graphs which apply Hooke's Law.

Momentum Formula

• Momentum = Mass x Velocity.
• The unit for momentum is kilogram meters per second (kg m/s).
• Momentum is always conserved.
• Momentum lost = Momentum gained.

Momentum Conservation

• In a closed system, momentum before an event equals momentum after the event.
• This applies to recoil, collisions, and explosions.

Types of Momentum Questions

• A bullet is fired from a gun; the momentum before and after are equal.
• A boy throws a ball forwards; the momentum before and after are equal.
• Two objects collide with each other; the momentum before and after are equal.

Elastic v Inelastic Collisions

• In elastic collisions, no kinetic energy is lost in the collision.
• In inelastic collisions, some kinetic energy is lost in the collision and is transferred to other forms of energy.

Relating Force, Momentum, and Time

• Force = Change in Momentum / Time (F = Δp / t).

Clockwise and Anti-Clockwise Moments

• Clockwise Moment = Anticlockwise Moment

Forces on Levers

• Work Done = Force x Distance.
• Energy transferred is equal to the work done.
• Moment = Force x Distance.

What is Electricity?

• Key equations, such as V = IR, apply.

Electrical Components

• Includes cells, batteries, resistors, thermistors, diodes, LEDs, voltmeters, and ammeters.
• A voltmeter is added in parallel.
• An ammeter needs to be added in series.

Resistance

• The resistance of a metal increases when the temperature is increased.
• Resistance increases because the positive ions vibrate more, stopping the flow of electrons.
• The opposite happens when the current goes through a thermistor.

Ohm's Law

• The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor.
• Not all materials and electric circuits have properties that apply Ohm's Law.
• A wire obeys Ohm's Law.
• A filament bulb does not obey Ohm's Law.
• A diode does not obey Ohm's Law.

Wiring Circuits

• In a series circuit, the current is the same through the entire circuit.
• Voltage is at its maximum at the power/energy source, but the current is split through the circuit.
• Parallel circuits increase the current through the circuit.

Electrical Quantities, Units, and Formula

• Charge: Measured in coulombs (C).
• Resistance: Measured in ohms (Ω).
• Voltage is current times resistance: V=IR.
• Charge is current times time: Q=IT.
• Work done is voltage times charge: W=VQ.

Power Equations

• Power: Measured in Watts (W).
• Power equals current times voltage: P=IV.

Alternating v Direct Current

• Alternating Current (AC): Current continuously changes direction.
• Direct Current (DC): Current flows in one direction only.

Efficiency and Energy

• Efficiency: How much energy input has been transferred usefully.
• Energy is Conserved: It cannot be created or destroyed, simply converted.
• A Sankey Diagram is also discussed.

Static Electricity: Charge Transfer

• Electrons are transferred from one place to another.
• Transferred due to friction.
• Opposite Charges Attract.

Static Electricity: Conductors

• Metals are good conductors; electrons can flow freely through the metal.

Static Electricity: Uses

• Spraying a bike: The bike frame is positively charged, so the paint needs to be negatively charged, meaning the paint repels itself.
• Inkjet Printer
• Photocopier
• Electrostatic Precipitator with smoke and dust.

Static Electricity: Dangers

• Planes flying become charged and need an earthed strip to make them safe.
• Lightning from the clouds to the Earth.

Wave Types

• Transverse Waves: Vibrations occur perpendicular to energy transfer (e.g., water, light).
• Longitudinal Waves: Vibrations occur parallel to energy transfer (e.g., sound waves).

Wave Properties

• Wave speed: Measured in meters per second (m/s).
• Frequency: Measured in Hertz (Hz).
• Wavelength: Measured in meters (m).
• Frequency equals 1/Time: Frequency = 1/T.

Labelling a Wave

• Amplitude: From the middle line to the top of the wave.
• Wavelength: The distance between two peaks or troughs.
• Wave equation: WaveSpeed = WaveFrequency x WaveLength.

Reflection and Sound Waves in Water

• Incident Angles: The waves hitting the surface.
• Those are the ones to measure and compare in waters.
• Refraction is about changing direction when it enters a new medium.

Optical Lens

• Real: An image that can be produced on a screen.
• Virtual: An image that cannot be produced on a screen.

Properties of an Image in a Plane Mirror

• The image will be the same size as the original object.
• It will be laterally inverted.
• Same color.
• It will be the same distance behind the mirror as you are standing in front of it.

Electromagnetic Spectrum: Formula

• When calculating the refraction index: n = sin l / sin r.
• Critical angles can be calculated by sine C = 1/n.

The Electromagnetic Spectrum

• Consists of these, from the lowest to highest frequency, lowest to shortest wavelength:
• Radio Waves
• Microwaves
• Infrared
• Visible - ROYGBIV
• Ultraviolet
• X-Rays
• Gamma Ray

Electromagnetic Spectrum: Uses and Properties

• Radio waves, microwaves, infrared, and visible light all use long wavelengths; the ones with the shortest use shorter wavelengths or can carry more intense frequencies.
• Radio waves: Communication.
• Microwaves: Communication.
• Infrared: Communication and can be used in toasters to heat food, emitting radiation.
• UV rays: Can help in UV lights to detect forgeries or authenticate money bills.
• X-Rays: Medical Industry for Body Scans.
• Gamma Rays: Sterilize Surgical Equipment effectively.

Electromagnetic Spectrum: Common Properties

• Vibrations are perpendicular to the direction.
• They all transfer energy.
• They travel at the speed of light (300 million m/s).

Energy

• Chemical - Energy stores, examples, food.
• Kinetic - To do with moving objects, such as a bus driving.
• Gravitational - Related to lifting objects, such as an apple tree.
• Elastic - Distorted objects returning to their original shape, such as rubber bands being fired.
• Nuclear - Reaction energy, such as in uranium.
• Thermal - Such as in a cup of tea.
• Magnetic - Energy is moved closer, such as a bar magnet.
• Electrostatic - Moving energy, such as charging clouds.
• Energy is conserved: energy cannot be destroyed or created, it's simply converted.
• Discusses Sankey Diagrams
• Electrical Input
• Useful Energy Out
• Wasted Energy Out.

Efficiency

• Efficiency = (Useful Energy / Total In) * 100.

Miscellaneous Questions

• Weight = Mass x gravity.

Components in Circuits - Rules

• Apply to either series or parallel circuits.
• Series circuits: the current is the same.
• Parallel circuits: the voltage is the same.
• Use the formula triangle and write it out for memory.

Static Electricity Basics

• Electron Transfer to start, and opposite charges are attracted.
• The key word is friction.
• Metal is a good conductor.

Formula's to Keep in Mind

Weight

• Weight is mass times gravity.
• Force is equal to weight.

KE

• KE is half mass times velocity squared.
• KE= 1 / 2 mv².

Heat Transfer - Types of Conduction

• Metals are very good conductors.
• Heat causes particles of air to gain kinetic energy.
• Bigger the energy; expand and less dense.

Convection

• Only happens in Liquids and Gases.
• Radiators are a prime example in a house that help get the temperature warm.

Radiation

• White/shiny surface reflects infrared radiation.
• Black surface absorbs more radiation.
• Radiation has less heat.
• A Thermos can be mentioned as an example.

Miscellaneous

• Electrical and renewable energy should increase.
• Fossil Fuels will run out.

Density and Pressure

• D = M/V.
• Different states have different properties:
• Solids - Very thick and close.
• Liquids - Moderately apart.
• Gases - Far apart.

Formula

• Pressure: Force times Area
• Pressure : Force / Area
• Particles with energy have to follow the rule of thumb.

Formulas

• D = M/V
• P = F/A
• Pressure increases with height, density, and gravity.
• P= h * G * density Height and size, does not effect density, because it stays constant

Basic Elements

• The elements that are magnetic: Iron, steel, cobalt, nickel.
• These are repelled on its end.
• Hard magnets: steel.
• Soft magnets: iron.

Magnetic - Motor

• Must be at right angles to each other.
• Fleming's Left Hand Rule:
• First finger = magnetic field.
• Second finger = current.

Electricity

• Electromagnetism is basically moving a wire, which creates a field and therefore creates current.
• Fleming's Right Hand Rule.
• It has to be used at 90 degrees.

Important Formula

• In transformers: Input / Output = primary turns / secondary turns.
• The Big Bang Theory gives redshift.

Doppler Effect

• Occurs where galaxies are moving, with the same effect as with sound.
• For light:
• When the wavelength gets longer, it is red.
• When the wavelength gets shorter, it's Blue.

Space

• The formula to keep in mind: V = 2 * pie * r / T.

Formulas to calculate speed, distance and time. Calculating speed from a Distance-Time Graph. Calculation of acceleration on a Velocity-Time Graph and applying SUVAT Equations.