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53 Cards in this Set
- Front
- Back
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What is speed? |
How fast you are going Measured in m/s or km/h or mph |
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What is velocity? |
Speed in a given direction eg. 20mph north |
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How to read a distance time graph? |
Gradient= speed Flat- stationary Straight- steady speed Downhill - going back towards starting point Steepening curve - speeding up (acceleration) Levelling of curve - slowing down (deceleration) |
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What is acceleration? |
How quickly velocity is changing The change in velocity can be in speed, direction or both = change in velocity ------------------------- time taken |
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How to read a velocity-time graph? |
Gradient= acceleration Flat- steady speed Uphill- acceleration Downhill- deceleration Area under the graph - distance travelled over all Curve - changing acceleration |
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What is gravity? |
The force of attraction between all masses Only noticed when one of the masses is really big It gives everything a weight |
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What is mass? |
The amount of matter in an object This has the same value anywhere in the world This isn't a force It is measured in kilograms with a mass balance |
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What is weight? |
It is a force caused by the pull of gravitational force The weight of an object differs depending where it is in the universe It is measured in newtons using a spring balance or newton meter = Mass X Gravity |
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What is a resultant force? |
The overal force acting on one object It decides the motion of the object It is the one force that replaces all other forces If there is a resultant force the object will changes it's motion and causes a change in the object's velocity |
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What happens if the resultant force is O? |
If the object is stationary the object will remain stationary and won't move If the object is moving it will continue to move at the same velocity |
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How do you work out acceleration? |
Acceleration = Force -------- Mass Measured in M/s squared |
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What are reaction forces? |
When two objects interact the forces they exert on each other are equal and opposite However if the objects mass you are pushing is smaller it will accelerate faster away than you |
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What is friction? |
A force that acts in the opposite direction to movement and slows objects down To travel at a steady speed the driving force needs to balance the frictional force Occurs from two surfaces in contact or when an object passes through a fluid (drag) |
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What happens to frictional forces when the speed of the object increases? |
The frictional forces also increase so the driving forces needs to increase more to keep a steady speed |
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How does terminal velocity occur? |
When falling objects first fall the gravity is a lot higher than the frictional forces so they accelerate As their speed increases however friction increases and this builds up This reduces their acceleration until the frictional force is equal to the accelerating force Therefore terminal velocity is reached - steady |
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What is stopping distance? |
The distance travelled in the time between the driver seeing the hazard and the car finally stopping still Thinking distance + braking distance |
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What is thinking distance?
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The distance the vehicle travels during the drivers reaction and until the driver pulls the brakes |
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What factors increase thinking distance? |
The speed the car is travelling at Tiredness, drugs, alcohol etc Bad visibility and distractions |
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What is braking distance? |
The distance the car travels after the driver has pressed the brakes until the car actually stops |
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What factors increase braking distance? |
The speed you are travelling at How good your brakes are The effectiveness of your tyre depth The road surface and weather conditions such as rain or ice |
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What is work done? |
When a force moves an object through a distance and energy is transferred Measured in Joules = Force x distance |
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What is gravitational potential energy? |
The energy an object has because of its vertical position in a gravitational field = Mass x gravitational field strength x height |
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What is kinetic energy? |
The energy of movement = 1/2 x mass x (speed)squared Kinetic E transferred = work done by brakes Kinetic energy gained = potential energy lost |
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How is energy transferred in a car? |
To slow a car down the kinetic energy needs to be converted to heat energy as friction causing the temperature of the brakes to increase |
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What is elastic potential energy? |
What work done to an elastic object is stored as Elastic object = any object that can go back to it's original shape after the force has been removed |
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What is extension? |
The length the spring stretches It is directly proportional to the load or force applied It is measured in metres = Force -------------------------- spring constant ( depends on the material ) |
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What is the limit of proportionality? |
The maximum force that can be applied to an elastic object before it can no longer extend proportional. |
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What is power? |
The rate of work done on an object Measured in Watts or Joules per second = Energy/ time |
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What is momentum? |
= Mass x velocity A vector quality that all moving objects have Measured in Kgm/s |
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What is the conservation of momentum? |
In a closed system momentum before an event is identical to the momentum after the event |
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What causes a change in momentum? |
Forces Larger force = larger change in momentum |
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What do brakes do? |
They reduce kinetic energy by transferring it to heat and sound energy - to slow the car down New regenerative braking systems use the kinetic energy to put the motor into reverse This slows the brakes and stores chemical energy in the vehicle's battery - more efficient |
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What do crumple zones do? |
They are the space at the front and back of a car designed to crumple on impact They convert the kinetic energy into other forms of energy They also increase the impact time decreasing the force felt by the passengers from the change in momentum |
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What do side impact bars do? |
They are strong metal tubes on door panels They direct he kinetic energy from the crash away from he passengers to other areas such as the crumple zones |
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What do seat belts and air bags do? |
SB They stretch increasing the time taken for the passenger to stop this reduces the force actin on the chest and some of the kinetic energy can be absorbed by the belt stretching The air bags slow the passengers down more gradually to prevent them from hitting a hard surface such as the windscreen |
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What is the power rating of a car based on? |
The size and design of the car engine The more powerful an engine the more energy it transfers from fuel every second - faster top speed it can travel Cars are designed to be aerodynamic and streamlined to minimise resistance |
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What causes a build up of static? |
Friction When certain insulating materials are rubbed together negative electrons are transferred |
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What happens on polythene rods and acetate rods? |
Polythene rods - electrons move from the duster to the rod Acetate rods- electrons move from the duster to the rod |
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What happens with charges attracting ...? |
Like charges repel Opposite charges attract These forces get weaker the further apart the two objects are from each other Charges move easily though conductors |
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What is current? |
The flow of electric charge around the circuit Measured in Amps = Charge ----------- Time |
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What is potential difference? |
The driving force that pushes current around the circuit Energy per coulomb of charge Unit : Volts Current x resistance |
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What is resistance? |
Anything in the circuit which slows down the current Measured in Ohms |
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What is charge? |
Measured in Coulombs It depends on current and time |
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What is an ammeter? |
A device that measured the current flowing through a component Must be placed in series In series current is the same everywhere In parallel current splits |
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What is a voltmeter? |
A device that measured the pf across a component Must be placed in parallel ( not around the variable resistor or the battery) In parallel - pd is the same everywhere |
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What happens to pd in a resistor? |
The pd is directly proportionate to the current through resistor |
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What happens to the resistance in a filament light? |
As the temperature increases the resistance increases |
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What is a diode? |
A special device made from semiconductor material It issued to regulate potential difference Current only flows in one direction so the diode has a extremely high resistance in the opposite direction |
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What is a LED? |
A light emitting divide It emits light when current flows in a forward direction |
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What is an LDR? |
A light dependent resistor In bright light the resistance falls In darkness the resistance if the highest |
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What is a thermistor? |
A temperature dependent resistors In hotness the resistance drops In cool conditions the resistance increases |
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What happens to pd and current in a series circuit? |
Current is the same everywhere Potential difference is split Resistance is split |
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What happens to pd and current in a parallel circuit? |
Pd is the same everywhere Current splits |
