2a) Motion, Energy and Electricity Flashcards
What does the gradient represent in a distance-time graph and a velocity-time graph?
In a distance-time graph, gradient means speed
In a velocity-time graph, gradient means acceleration
Define the difference between speed and velocity
Speed is how fast you’re travelling
Velocity is speed in a direction or with a vector
What is gravity?
The force of attraction between all masses
How do you work out weight using mass and gravitational field strength?
W=mxg
What is the resultant force?
Overall force of an object
If there is a resultant force acting on an object, what will happen to the object?
Object will change it’s state of rest or motion or change its velocity (acceleration)
What happens is the resultant force on a stationary object is zero?
Object will remain stationary
If there is no resultant force on a moving object, what will happen?
Object will keep moving in the same direction at the same velocity
No change in velocity
When two objects interact, the forces they exert on each other are…..?
Equal and opposite
If an object has no force propelling it along, why would it slow down and stop?
Friction acts in the opposite direction to movement
How can you reduce drag or air resistance by changing the shape of a vehicle?
Streamlined
What happens to drag as speed increases?
Drag increases
What does the terminal velocity of falling objects depend on?
Their shape and area
What is stopping distance?
Distance covered in the time between the driver spotting a hazard and the vehicle coming to a complete stop
Sum of thinking distance and breaking distance
What things affect thinking distance?
How fast you’re going - faster speed = further distance
Brain state - affected by tiredness, drugs, alcohol, careless attitude
Bad visibility and distractions
What is thinking distance?
The distance the vehicle travels during the driver’s reaction time
What is braking distance?
The distance a car travels under the braking force
What is braking force affected by?
How fast you’re travelling - faster speed = further distance
Quality of brakes
Thickness of tyres - thicker tyres = better braking distance
Grip - affecting road surface, weather, tyres
What happens regarding forces when a force moves an object through a distance?
Energy is transferred
Work is done
How do you calculate work done?
Force x distance
What is gravitational potential energy?
Energy that an object has because of its vertical position in a gravitational field
What two things does kinetic energy depend on?
Mass - more it weighs, faster speed, bigger kinetic energy
Speed - faster, bigger kinetic energy
What does the conservation of energy state?
Energy can never be created it destroyed only converted into different forms
When something falls, what is it’s potential energy converted into?
Kinetic energy
What is an elastic object?
Any object that can go back to its original shape after a force has been removed
What is extension measured in?
Metres
What is elastic potential energy?
Potential energy stores in an elastic object which has had work done to change it’s shape
What is power?
The rate of doing work or the time taken for energy to be transferred
What is power measured in?
Watts (joules per second)
What is current?
Rate of flow of electric charge around a circuit
What is potential difference?
The driving force that pushes the current round
The work done (energy transferred) per coulomb of charge
What is resistance?
Anything in a circuit which slows down the current
What happens to resistance when temperature increases?
Resistance increases
What is a diode made from?
Semiconductor material such as silicon
What is a diode for?
Used to regulate potential difference in circuits
Lets current flow freely in one direction but not in the other
High resistance in reverse direction
Why are LEDs better than normal lighting?
They use a much smaller current
What does LED and LDR stand for)
Light Emitting Diode
Light Dependant Resistor
What is an LDR
Resistor that is dependant on the intensity of light
Bright light - resistance falls
Darkness - high resistance
What is a thermistor?
Temperature dependant resistor
Hot - resistance falls
Cold - high resistance
In what type of circuit is the potential difference shared across the components?
Series circuit
V = v1 + v2 + …..
In what type of circuit is the current the same everywhere?
Series circuit
How do you work out the resistance in a series circuit?
Total resistance = sum of all the resistances
If you add more bulbs to a series circuit what will happen to their light?
Light up less brightly than before
Because p.d is shared in series circuits
In what type of circuit is the potential difference the same across all components?
Parallel circuits
When something falls, what happens to it’s potential energy?
Converted into kinetic energy
Further it falls - faster it goes
What is the limit of proportionality?
Maximum force that the elastic object can take and still extend proportionally
