Physics 2a- Motion,energy And Electricity Flashcards
Distance time graphs
Gradient=speed Flat sections- stopped Straight uphill/downhill- steady speed Steeper-faster Downhill-back to starting point Curves- acceleration/deceleration Steepening curve- speeding up Levelling off curve- slowing down
Acceleration
Acceleration is how quickly the velocity is changing. This change in velocity can be change in speed/direction
Formula- acceleration = change in velocity divided by time taken
Velocity time graphs
Gradient= acceleration
Flat sections-steady speed
Steeper- greater acceleration or deceleration
Uphill- acceleration
Downhill- declaration
Area under any section of graph- equal to distance traveled in time interval
Curve- changing acceleration
Weight mass and gravity
Gravitational force- force of attraction between all masses
Mass - amount of stuff in a object
Weight- pull of gravitational force
Formula- weight= mass X gravitational field strength
Resultant forces
Resultant force is the overall force on a point or object
Example- stationary teapot- all forces balance
A resultant force means a change in velocity
Example- car
Forces and acceleration 1
If the resultant force on a stationary object is zero the object will remain stationary
If there is no resultant force on a moving object. It will just carry on moving at the same velocity
If there is a non zero resultant force, then the object will accelerate in the direction of the force
Forces and acceleration 2
Formula- f=ma or a = f/m
Reaction forces are equal and opposite
When two objects interact the forces they exert on each other are equal and opposite
Frictional force and terminal velocity
Friction slow things down
Example- resistance or drag for fluids
As speed increases so does drag
Objects falling through fluids reach a terminal velocity
The terminal velocity of falling objects depends on their shape and area
Stopping distances
Total stopping distance- distance leered in the time between the driver first spotting the hazard and the vehicle coming to a stop
Thinking distance- affected by speed and alertness
Braking distance - affected by speed,condition of brakes, condition of tyres, grip
Work and potential energy
When a force moves an object through a distance energy is transferred and work is done.
Formula- work done= force X distance
Formula 2- gravitational potential energy= mass X g X height
Kinetic energy
Formula- Kinetic energy= 1/2 x mass X speed squared
Car formula- kinetic energy transferred= work done by brakes
Falling objects formula- kinetic energy gained= potential energy lost
Forces and elasticity
Work done to an elastic object is stored as elastic potential energy. Extension of an elastic object is directly porportional to force, but stops working when the force is great enough
Power
Formula- power = work done divided by time taken
Momentum and collisions
Formula- momentum= mass X velocity
Forces causes changes in momentum. When a force acts on a object causes change in momentum
Car design and safety
Crumple zones at the front and back allow kinetic energy to be converted into other forms of energy as it changes shape.
Side impact bars- help direct kinetic energy of the crash away from passengers
Seat belts - reduce forces acting on chest when in a crash
Air bags - prevent from hitting hard surfaces in the car
