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
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  • 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
            • Gradient - velocity
            • Velocity - Time graphs
              • Gradient - acceleration
                • Area beneath - displacement
              • Constant Acceleration Equations
                • v = u + at
                • s = ((u + v) / 2) x t
                • s = ut + 1/2 a t²
                • v² = u² + 2as

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