Flashcards in P2a Deck (51):
How fast you are going without direction
How fast you are going with direction
How quickly a velocity is changing
The overall force on a point or object
An object needs...
A force to start moving
No resultant force means...
No change in velocity
A resultant force means...
Reaction forces are...
Equal and opposite- when two objects interact, the forces they exert on each other are equal and opposite
Friction is always there to...
Slow things down
Friction acts in the...
Opposite direction to movememt
Increases as the speed increases- the faster your going the more drag you have
When an object falls, the gravity is much greater than the frictional force - this leads to acceleration
As the speed increases, the friction builds up
This reduces the acceleration until eventually the frictional force is equal to the accelerating force - it remains at a steady maximum speed
Breaking distance + thinking distance
The distance the vehicle travels during the drivers reaction time
Thinking distance can be affected by...
How fast your going
How tired you are
Whether you have had alcohol or drugs
The distance the vehicle travels under the braking force
Breaking distance can be affected by...
How fast your going
How good your tires are
How good your breaks are
How good the grip is - road surface, weather conditions and tires
Work done definition
When a force moves an object through a distance, energy is transferred and work is done
Gravitational potential energy
Energy due to height
Measured in joules
Energy of movement
Kinetic energy depends on...
The speed and mass of an object
When a car is stopping...
The kinetic energy is converted into heat energy as friction between the wheels and the break pads, causing the temperature to increase
Convert their potential energy into kinetic energy
Kinetic energy gained= potential energy lost
Forces causes change in momentum
When a force acts on an object, it causes a change in momentum
A larger force means a faster change in momentum
Likewise - if someone's momentum changes very quickly, the force on the body will be very large
Electric or hybrid cars have...
Regenerating braking system
Regenerating braking system
Break puts vehicles motor into reverse. This means wheels slow down
At the same time the motor acts as an electrical generator, converting kinetic energy into electrical energy that is then stored as chemical energy in the vehicles battery
Cars are designed to convert kinetic energy safely in a crash
In a crash, there is a big change in momentum over a short amount of time, this means people in the car experience a large amount of force that could be fatal
Cars are designed to...
Convert the kinetic energy of the car in a safe way. They do this by increasing the time over which momentum changes happen, therefore reducing the force felt on the person
Kinetic energy is converted into other forms of energy by the car body as it changes shape
Increases the impact time, decreasing the force produced by the change in momentum
Side impact bars
Strong metals bars in the car door panel- this directs the kinetic energy away from the passenger
Increases the time taken for the change in momentum, reducing the force acting on the chest
Some kinetic energy is absorbed by the seat belt stretching
Allows you to slow down more gradually- less force due to a slower change in momentum
Also prevents you from hitting hard surfaces inside the car - soft landing
Static electricity build up
Build up of static electricity is caused by friction
How static electricity works
When certain insulating materials rub together, negatively charged electrons will be scraped off and dumped on the other
This leaves a positive static charge on one and a negative static charge on the other
Electrically charged objects attract small objects placed near them
Is the flow of electric charge round the circuit, current will only flow through a component if there is a potential difference across the component
Unit - Ampere, A
Potential difference/ voltage
The difference in energy carried by an electrical charge between two points in a circuit. It's also the driving force that pushes the current around
Units - Volts, V
Anything in the circuit which slows the flow down
Unit - Ohms
The bigger the potential difference...
The higher the current.
This is because the current flows from a high energy point to a low energy point
Must be placed in the series
Can be placed anywhere in the series
Measures the currents flowing through the component
Measures potential difference across the component
Must be placed in parallel around the component under the test
Varying the resistor...
Alters the current flowing through the circuit
Different resistor graph
The current through a resistor is directly proportional to the potential difference
Current will only flow through a diode in one direction
Emits light when a current is flowing through it in a forward direction
They work with a much smaller current than filament bulbs
It's used to regulate the potential difference in a circuit
Only let's current flow in one direction
A light sensitive resistor
In bright lights the resistance falls
In darkness the resistance is highest
Heat sensitive resistor
In hot conditions the resistance falls
In cool temperatures the resistance is highest
Series circuit rules
Potential difference is shared
Current is the same everywhere
Resistance adds up
Cell voltages add up
Parallel circuit rules
Potential difference is the same across all components
Current is shared between branches