paper 1

• air resistance


  slows a falling object

  is a frictional force

  opposes the motion of objects moving through air
• circular motion


  centripetal forces

  • when an object moves in a circular direction it has a constant speed but is constantly changing direction
  • this means there is a constant change in velocity and it is always accelerating
  • the resultant force always acts towards the centre of the circle
• what is weight


  the force acting downwards on an object due to gravity
• mass


  the amount matter it contains
• weight calculation

  weight = mass x gravitational field strength
• what is inertia?


  Inertia is a measure of how difficult it is to change the object's motion. An object with a high mass has more inertia than an object with less mass.
• thinking distance


  the time between when a driver realises they need to put the brakes on and when they actually apply the brakes
• reaction speed


  the time it takes the driver to react to a situation
• braking distance


  the distance the car travels between the driver applying the brakes and the car stopping
• thinking distance effectors


  • tiredness
  • distractions
  • drugs / alcohol
• braking distance effectors


  • weather
  • tyres
  • initial car speed
• Every measurement or quantity has a unit
• Units

  • Meters for distance
  • Seconds for time
• Prefixes

  • Used for very big or very small numbers
  • Generally go up or down in thousands times
  • Apart from centimeters and decimeters
• Converting units

  1. Think do I want a bigger number multiplied by the conversion factor or a smaller number

  2. Divide by the conversion factor
• Prefixes in standard form

  • Positive powers for anything bigger than a meter
  • Negative powers for anything smaller than a meter
• Force

  • Any push or pull
  • Can be contact forces (physically touching)
  • Can be non-contact forces (like magnetism, electrostatic, gravity)
• Representing forces

  With vectors (arrows showing direction and magnitude)
• Finding resultant force

  1. Technically adding the vectors

  2. If in opposite directions, one must be negative

  3. If at right angles, use Pythagoras
• Balanced forces

  • Forces add up to zero
  • Object will not accelerate, stays at constant velocity
• Scalar

  Measurement or quantity with magnitude but no direction
• Vector

  Measurement or quantity with both magnitude and direction
• Examples of scalars and vectors

  • Scalars: distance, speed, weight
  • Vectors: displacement, velocity, force
• Weight

  • Force due to gravity acting on an object
  • Calculated as mass * gravitational field strength (9.8 N/kg or 10 N/kg)
• Lifting an object at constant speed

  Upward force must equal the weight
• Work done

  • Energy transferred by a force
  • Calculated as force * distance moved
• Gravitational potential energy

  Calculated as mass * gravitational field strength * height
• Moment

  • Turning force
  • Calculated as force * perpendicular distance to pivot
• If moments turning clockwise and anticlockwise are balanced, object will not turn
• Gears

  Application of moments to increase the moment produced
• Speed and velocity

  • Measured in m/s
  • Velocity has direction (can be positive or negative)
• Calculating speed and velocity

  Distance or displacement over time
• Acceleration

  • Change in speed divided by time
  • Unit is m/s^2
• Acceleration due to gravity

  Constant 9.8 m/s^2 downwards
• Velocity-time graph

  • Gradient gives acceleration
  • Area under graph gives distance traveled
• Newton's equations of motion

  Used to predict object's motion when accelerating
• Variables in Newton's equations

  • s = displacement
  • u = initial velocity
  • v = final velocity
  • a = acceleration
  • t = time
• Newton's first law

  No resultant force, motion is constant
• Inertia

  Tendency for an object's motion to stay constant unless acted on by a resultant force
• Newton's second law

  Unbalanced forces, F = ma