Physics Flashcards
Difference of speed and velocity
Equation for average speed
Speed is just how fast you are going with no regard to direction.
Velocity is speed and direction.
Average speed = distance moved /time taken
Acceleration
Acceleration=change in velocity/time taken
Unit : m/s^2
Velocity time graphs.
What does a straight horizontal line show ?
Uphill line? Curve?
Shows how an objects velocity changes over time.
Flat horizontal lines means steady speed.
Uphill means acceleration and downhill means deceleration.
Curve is changing acceleration
Distance time graphs
What does a flat horizontal line represent ?
Steeper line?
Curve?
Flat line means it’s stopped
A steeper graph means it’s going faster
Curves represent acceleration
What is the force of attraction between all masses?
What is the difference between Mass and Weight?
What is weight measured in? Mass?
What is the equation linking mass weight and gravity?
Gravity.
Mass is the amount of stuff in an object, is it NOT a force.
Weight is caused by the pull of gravity. So it will be difference weight on the moon than on earth. Weight it a force measured in Newton’s.
Weight = mass x gravitational field strength
W= m x g
Name the different types of force.
What three ways does friction occur ?
Gravity or weight. Reaction force Electrostatic force Thrust Drag or air resistance Lift Tension
The three ways friction occurs is: friction between solid surfaces which are gripping
Friction between solid surfaces which are sliding past each other.
Resistance or drag from fluids and gases.
State the three laws of motion.
1st law : so long as the forces on an object are all balanced, then it will stay still, or else if it’d already moving it will just carry on at the same velocity- as long as all forces are balanced.
2nd law: if there is an unbalanced force, then the object will accelerate in that direction.
3rd law: if object a exerts a force on object b, object b will exert the equal and opposite force on object a.
The equation for resultant force.
Resultant force= Mass x acceleration
F=ma
What are vector quantities? What are scalar?
List four examples of both vector and scalar.
Vector quantities have force and direction.
Scalar only have size and No direction.
Vector; force, velocity, acceleration, momentum.
Scalar; mass, temperature, time, length.
Explain why an object falling through the sky will stop accelerating.
When an object starts falling it has much more acceleration than resistance slowing it down. As the velocity increases, the resistance builds up.
This resistance force gradually reduces the acceleration until eventually the resistance force is equal to the accelerating force, it has reached it maximum velocity or terminal velocity.
Explain Hooke’s law
The extension of a stretched wire is proportional to the load or force.
What is the equation for stopping distance?
What is thinking distance? What factors affect this?
What is braking distance? What factors affect this?
Stopping distance= thinking distance + braking distance.
Thinking distance is the distance the car travels in the time between the driver noticing the hazard and applying the breaks. This can be affected by how fast you are going and your reaction time (drugs, age, alcohol)
Braking distance is the distance the car travels during its deceleration whilst the brakes are being applied. This is affected by how fast you are going, the mass of the vehicle, how good your brakes are and how good the grip is.
Momentum equation
Momentum = mass x velocity
Forces cause changes in momentum equation
What designs in cars help slow down people over a period of time in a crash?
Force(N) = change in momentum/time
Crumple zones crumple on impact, increasing the time taken for the car to stop.
Seat belts stretch slightly,increasing the time taken for the wearer to stop. Reducing the forces on the chest.
Air bags also slow you down more gradually
Equation of moment
Where does the center of gravity hang?
Moment(Nm) = Force x perpendicular distance between line of action and pivot.
Below the point of suspension
What is current? Voltage? Resistance?
What is an ammeter ? The voltmeter ?
Current is the rate of flow of charge around a circuit.
Voltage is what drives the current round a circuit.
Resistance is anything that slows the flow down in the circuit.
Ammeter measures in amps, must be places in series but never parallel the component.
Voltmeter measures in volts, must be placed in parallel around the components under test
Formula linking V and I
Voltage= Current x Resistance
What is an LED? LDR?
Light-emitting diodes emit light when a current flows through them.
Light-dependent resistor changes it’s resistance depending how much light falls on it. In bright light the resistance falls and in darkness the resistance is highest.
Difference between series and parallel circuits?
Series is all or nothing while parallel has independent components.
What is the formula for charge?
Charge = current x time
Give the definition of the volt.
One volt is one joule per coulomb
Equation for energy transferred.
Energy transferred = charge X voltage.
What color is the live, neutral, and earth wire?
Live wire is brown.
Neutral wire is blue.
Earth wire is green yellow.
What are the volts of the live, neutral, earth wire?
The live wire alternates between a high ve and -ve of about 230v.
Neutral wire is always at 0v.
Earth wire is just for safety.
How does a fuse work?
A fault in the live develops sending a surge thro the earth wire, this surge blows the fuse which cuts off live supply.
Give the formula of electrical power
Electrical power = current X voltage.
The equation involving frequency, wavelength and speed.
Speed = frequency x wavelength.
What are transverse and longitudinal waves?
Give 3 examples of each.
Transverse waves, most waves. In transverse waves the vibrations are at 90 degrees to the direction energy is transferred by the wave.
Longitudinal wave vibrations are along the same direction as the wave transfers energy.
Transverse: light and all other EM waves. Waves on strings, ripples on water.
Longitudinal: sound and ultra sound. Shock waves, slinky when you push the end,
What are wavefronts?
Wavefronts are imaginary planes that cut across all the waves connecting the points on adjacent waves which are vibrating together.
What is the Doppler effect?
The Doppler effect makes waves appear longer or shorter.
What are the seven types of EM waves? Name them in increasing frequency and decreasing wavelength.
Radio waves Microwaves Infrared Visible light Ultra violet X rays Gamma rays.
Give the uses of radio waves, microwaves, infrared, and light signals .
Radio waves are used mainly for communications.
Microwaves are used for satellite communication and heating food.
Infrared radiation is used for heating and to monitor temperature.
Light signals can travel through optical fibers.
Give the uses of visible light, ultra violet, x rays, and gamma radiation.
Visible light is useful for photography.
Ultraviolet is used in fluorescent lamps
X rays let us see inside things.
Gamma radiation can sterilizing medical equipment and sterilizing food.
State the law of reflection
Angle of incidence = angle of reflection
Define refractive index
Refractive index = speed of light in a vacuum/ speed of light in that material
Smells law states…
N = sin i/ sin r
What are sound waves?
What is the human ear capable of hearing?
How does the speed of sound change when in different densities?
Sound waves are longitudinal waves caused by vibrating objects.
The human ear is capable of hearing frequencies between 20 Hz and 20 000 Hz
Speed travels faster in solids that in liquids, and faster in liquids than in gases.
Name the 8 energy stores.
Kinetic Thermal Chemical Gravitational potential Elastic potential Electrostatic Magnetic Nuclear
Name the four main ways energy is transferred .
Mechanically
Electrically
By heating
By radiation
What is the principle of conservation of energy?
Energy can be stored, transferred between stores and dissipated but it can never be created or destroyed. The total energy of a closed system has no net change
When is energy useful
Energy is only useful when it is transferred from one store to a useful store.
Equation for efficiency
Efficiency= useful energy output/ total energy output X 100
Define thermal conduction
Thermal conduction is the process where vibrating particles transfer energy from their kinetic energy store to the Kinetic energy stores of neighboring particles.
What is conduction and what is convection.
Conduction is the main form of energy transfer by heating in solids.
Convection is the main form of energy transfer by heating in liquids and gases.
Define convection
Convection occurs when the more energetic particles move from the hotter region to the cooler region - and transfer energy as they do.
Define ‘work done’.
When a force moves an object through a distance, WORK IS DONE on the object and ENERGY IS TRANSFERRED.
Formula for work done
Work done = Force x Distance moved
Formula for power
Power = work done / time taken
Define power
Power is the rate at which energy is transferred
Formula for energy in kinetic energy store
Formula for energy in G.p energy store
Energy in kinetic energy store = 1/2 x mass x (speed) ^2
GPE = mass x gravitational field strength x height
What are the four non renewable sources
Coal
Oil
Natural gas
Nuclear fuels
Formula for density
Pressure
And pressure difference
Density= mass/volume
Pressure = force/area
Pressure differences= height x density x gravitational field strength
What is absolute zero , freezing point, and boiling point of water in Celsius and kelvin
Absolute zero is -273 C, freezing point is 0 C, and boiling point is 100 C
Absolute zero 0 K, freezing point is 273 K, and boiling point is 373 K
