AQA GCSE Physics Unit 2 Mindmap

Motion
1. Distance-time graphs
  1. Helps us describe the motion of an object
  2. Speed
    1. The distance travelled each second
  3. The gradient represents the speed of an object
    1. Speed=Distance over time
2. Velocity and acceleration
  1. Velocity is speed in a given direction
    1. Measured in m/s
    2. If the velocity of an object changes we say it accelerates
      1. Measured in m/s squared
  2. Deceleration
    1. A negaitve acceleration
3. Velocity-time graph
  1. Gradient represents acceleration
  2. The steeper the gradient the greater the acceleration
  3. If the line is horizontal the acceleration is zero!
  4. If the gradient is negative the object is decelerating
  5. The area underneath the graph shows the distance travelled
  6. An object travelling at a steady speed may be accelerating
    1. If it is changing direction
Forces
1. Forces between objects
  1. Newtons third law
    1. Every action has an equal and opposite reaction
  2. Measured in Newtons (N)
  3. A force can change an objects motion or state of rest
    1. Forces have both...
      1. Size
      2. Direction
2. Resultant force
  1. The combined effect of all forces acting on an object
  2. If an object is at a state of rest
    1. It will stay at rest if the resultant force is zero
    2. It will accelerate in the direction of the resultant force
  3. If an object is moving
    1. Carry on moving in the same direction if the resultant force is zero
    2. Accelerate in that direction
    3. In the opposite direction to the resultant force it will decelerate
3. Acceleration
  1. A resultant force always causes an acceleration
  2. If there is no acceleration in a situation there is no resultant force
  3. A change in velocity
    1. A resultant force is needed to change the direction of an object
  4. The bigger the mass of an object...
    1. The bigger the force needed to give a particular acceleration
4. On the road
  1. Stopping distance
    1. Thinking distance + Braking distance = stopping distance
  2. Thinking distance
    1. Factors affecting
      1. Alcohol
      2. Age
      3. Drugs
      4. Tiredness
    2. The distance travelled in the time it takes the driver to react
      1. Their reaction time
  3. Braking distance
    1. Factors affecting
      1. Road conditions
      2. Weather conditions
      3. Worn tires
      4. Worn brakes
    2. The distance travelled in the time it takes for the brakes to act
  4. Travelling at a steady speed
    1. The driving forces are equal and opposite
    2. Resultant force is zero
5. Falling objects
  1. Falling freely
    1. Resultant force acting on it is gravity
      1. Object accelerates at 10m/s squared if close to the earths surface
  2. Objects falling in fluids
    1. fluid exerts a drag force on the object
      1. Resists its motion
    2. The faster it falls..
      1. the bigger the drag force
        until it equals the weight of the object
        The resultant force is now zero
        Stops accelerating
        Moves at a constant velocity called the terminal velocity
  3. The force of gravity on objects
    1. Weight
      1. Don't confuse with mass
        The amount of matter in an object
    2. If an object isnt falling g is called the gravitational field strength
      1. N/Kg
6. Stretching and squashing
  1. Increase of length of a spring is its extension
  2. Objects that regain their shape after work was done to change its shape are said to be elastic
    1. Hooke's law
      1. The extension of a spring is directly proportional to the force applied, provided the limit of proportionality isn't esceeded
        Spring constant is the force per unit extension needed to stretch
      2. The stiffer a spring the greater its spring constant
      3. When elastic objects are stretched work is done and stored as elastic potential energy
Work, energy and momentum
Current electricity
1. Electrical charges
  1. Two insulating materials
    1. Electrons transferred/rubbed off and deposited
      1. Lose electrons
        Positively charged
      2. Gains electrons
        Negatively charged
2. Series
  1. P.d is total of all components added together
  2. Same current across each component
  3. How ammeters are connected
3. Parallel
  1. P.d. is the same across each component
  2. total current is all components added together
  3. If one part breaks the rest still works
  4. The bigger the resistance through a component the less current can flow through it
  5. Voltmeter connected like this
4. Current potential difference graphs
  1. Show how current through a component varies with potential difference across it
    1. filament bulb
      1. A curve
      2. Resistance increases as current increases
        Because resistance increases as temperature increases
      3. Reversing the p.d. makes no difference to the curve
    2. Diode
      1. Current only flows in one directiom
        In the reverse direction it has a very high resistance so the current is zero
    3. As light gets brighter on an LDR resistance decreases
    4. As temperature of a thermistor goes up the resistance goes down
5. Ohms law
  1. Current is directly proportional to the potential difference through a component
6. Resistance is the opposition to current flow
Mains electricity
Radioactivity
Nucleus energy

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