Physics Unit 1

My mindmap of the whole of OCR Physics A Unit 1.

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• Created by: Emily
• Created on: 17-04-13 11:52
• Physics Unit 1
• Motion
• Physical Quantities and Units
• SI Units
• Mass - kg
• Length - m
• Time - s
• Temperature - K
• Current - A
• Amount of substance - mol
• Prefixes
• pico, nano, micro, milli, centi, kilo, mega, giga, tera
• -12, -9, -6, -3, -2, 3, 6, 9, 12
• p, n, µ, m, c, k, M, G, T
• Scalar and Vector
• Scalar - magnitude but not direction
• temperature
• speed
• Speed = distance per unit time
• Instantaneous speed - speed at a given instant of time
• time
• Constant Acceleration Equations
• displacement
• velocity
• Velocity - displacement per unit time
• acceleration
• Acceleration - rate of change of velocity
• (v - u) / t
• Free Fall
• g = 9.81ms-²
• Direct approach of measuring g
• Trap door and electromagnet method
• Indirect approach of measuring g
• Measuring the time taken for a pendulum to complete a full swing
• Affected by air resistance
• Acceleration of free fall is vertically down towards the centre of the earth
• Non-constant (non-linear) acceleration
• v = u + at
• s = ((u + v) / 2) x t
• s = ut + 1/2 a t²
• v² = u² + 2as
• distance
• mass
• x or / by scalar gives a scalar
• Vector - magnitude and direction
• velocity
• Velocity - displacement per unit time
• displacement
• acceleration
• Acceleration - rate of change of velocity
• (v - u) / t
• Free Fall
• g = 9.81ms-²
• Direct approach of measuring g
• Trap door and electromagnet method
• Indirect approach of measuring g
• Measuring the time taken for a pendulum to complete a full swing
• Affected by air resistance
• Acceleration of free fall is vertically down towards the centre of the earth
• Non-constant (non-linear) acceleration
• force
• x or / a vector by a vector can give a vector or a scalar
• vector x scalar always gives a vector
• Vector calculations
• Vector is represented with an arrow
• Vector triangles are used to calculate the resultant of two vectors
• Pythagoras - a² = b² + c²
• Resolution of vectors
• vectors have a horizontal and vertical component
• horizontal = x sin angle
• vertical = x cos angle
• SohCahToa
• Forces in action
• Force
• Gravitational Force
• Between two objects with mass, e.g. weight
• Weight is the gravitational force on a body
• W = mg
• Centre of gravity
• Where the entire weight of an object can be considered to act as a single force.
• Magnetic Force
• Between two magnetic objects - the force between moving charges
• Electrical force
• Between chnarged objects - this is responsible for all interactions between objects
• Every object is made of positive protons and negative electrons which exert an electrical force on one another when they collide.
• e.g. Hand touching table
• Force causes acceleration, when an object has no resultant force, it has no acceleration
• Acceleration is proportional to force, if the mass is constant
• F = ma
• mass
• Acceleration is inversely proportional to mass, if the force is constant
• F = ma
• Unit of force is the Newton (N)
• 1N is the force that causes a mass of 1kg to have an acceleration of 1ms every second
• Resistive force - drag
• Depends on - velocity, cross sectional area, roughness of surface, shape.
• Occurs when an object tvels through a fluid
• A fluid is a liquid or gas
• The drag on an object increases as it accelerates
• Equilibruim
• Zero resultant means zero acceleration for an object, and it is said to be in equilibruim
• An object moving at constant velocity is in equilibruim
• Turning Forces
• Couple
• A pair of equal and parallel but opposite forces, which tends to produce rotation
• Resultant is always zero
• Torque
• torque = one of the forces x the perpendicular distance between the forces
• Describes the turning effect of a couple
• measures in Nm
• Produces a rotation rather than a linear motion. Describes items such as electrical drills
• Moment
• The moment of a force is the force x the perpendicular distance from a stated point
• The moment of a force is the turning effect of a single force
• Measured in Nm
• Principle of Moments
• For a body in rotational equilibrium, the sum of the clockwise moments equals the sum of the anticlockwise moments
• Density
• ? = Mass per unit volume
• kg m3
• Pressure
• Force per unit area
• pressure = h?g at a depth in fluid
• Measured in Pascals (Pa)
• Floating
• Pressure on the bottom of an object keeps it afloat
• force upwards = weight downwards
• Cars
• work done by a vehicle against its braking force = force x distance
• Also called the kinetic energy of a vehicle
• stopping distance = thinking distance + braking distance
• Crumple Zones
• Parts of the car designed to collapse in a collision
• increase the distance over which the force is acting so the average force is less
• Seat Belts
• Increases the distance over which the force can act
• Airbags
• Keeps your mass in your seat to stop collisions with rigid objects
• Keeps your mass in your seat to stop collisions with rigid objects
• Airbags
• GPS
• Use trilateration to determine positioning of an object on the earth
• Work and Energy
• Work
• work = force = distance moved in the direction of the force
• Measured in Joules (J)
• 1J is the work done when a force of 1N moves its point of application 1m in the direction of the force
• Power is the rate of doing work
• Power
• measured in joules per second = watts (W)
• Kilowatt-hours (kWh)
• Equivalent to using 1000W of power for an hour.
• Energy
• The stored ability to do work
• Kinetic energy
• Where movement is taking place
• An object has speed
• Work an object can do by virtue of its speed
• kinetic energy = 1/2mv²
• Falling objects
• Gravitational Potential energy
• Where an object is at a high level in the Earth's gravitational field
• The energy stored in an object (the work an object can do) by virtue of its position in a gravitational field
• gravitational potential energy = mgh
• velocity of a falling object  = Square root of 2gh
• Potential energy
• Fields where electric, magnetic, gravitational and nuclear forces exist.
• Gravitational Potential energy
• Where an object is at a high level in the Earth's gravitational field
• The energy stored in an object (the work an object can do) by virtue of its position in a gravitational field
• gravitational potential energy = mgh
• Conservation of energy
• Energy may be converted from one form into another, but it cannot be created or destroyed.
• Deformation  of materials
• Elastic
• When it regains its original shape
• Once the elastic limit has been passed, the stretch becomes permanent
• Up to the elastic limit, the graph has a straight line
• Tension - Extension graph
• Graphs
• Past the elastic limit, the graph is a curve
• When  it is permanently distorted
• The  stretching of a wire
• Plastic
• When  it is permanently distorted
• Tensile Forces
• Forces that  stretch objects such as wires.
• cause tension in the object
• Hooke's Law
• Elastic
• When it regains its original shape
• Once the elastic limit has been passed, the stretch becomes permanent
• Up to the elastic limit, the graph has a straight line
• Tension - Extension graph
• Graphs
• Past the elastic limit, the graph is a curve
• The  stretching of a wire
• The extension of an elastic body is proportional to the force that causes it
• F = kx where k is the force constant
• Elastic potential energy of the wire = 1/2kx²
• Compressive Forces
• Forces that  squeeze an object
• Young modulus
• stress / strain
• stress is the force per cross sectiona area
• stress = F/A
• measured in pascals (Pa)
• strain is extension per unit length
• strain = x/L
• No units
• The ratio between stress and strain
• Categories of materials
• Ductile
• Can be drawn out into a wire - plastic deformation.
• takes a lot of strain before it breaks
• Brittle
• distort very little but will snap if subjected to large stress
• Polymetric
• such as rubber, doesn't break
• Graphs
• Displacement - Time graphs
• Velocity - Time graphs
• Area beneath - displacement
• Constant Acceleration Equations
• v = u + at
• s = ((u + v) / 2) x t
• s = ut + 1/2 a t²
• v² = u² + 2as