physics paper 2

• Units you should know

  • Forces (including weight) in Newtons
  • Mass in kilograms
  • Distances in meters
  • Speeds/velocities in meters per second
  • Times in seconds
  • Gravitational field strength in Newtons per kilogram
  • Work done in joules
  • Acceleration in meters per second squared
  • Momentum in kilogram meters per second
  • Frequency in hertz
  • Magnetic flux density in Teslas
  • Current in amps
  • Potential difference in volts
• Scalar quantities


  Quantities that don't have a particular direction, just a magnitude or size (e.g. temperature, energy, speed)
• Vector quantities


  Quantities that have both magnitude and direction (e.g. velocity, momentum, forces)
• Vectors can be represented by arrows, where the length corresponds to the size and the direction corresponds to the direction of the quantity
• Free body diagrams show the forces acting on an object, represented by arrows, with no other details drawn
• Contact forces


  • Friction
  • Air resistance
  • Tension
  • Normal contact force
• Non-contact forces include weight (due to gravity), electrostatic forces, and magnetic forces
• Newton's third law


  • For every action there is an equal and opposite reaction
  • The two forces are always of equal size
  • They are the same type of force (both pushes or both pulls)
  • They act in opposite directions
  • They act on the other object
• Mass


  How much matter or how many atoms an object is made from, measured in kilograms
• Weight


  The force experienced by an object due to gravity, measured in Newtons
• Weight is proportional to mass, so as mass doubles, weight doubles
• Weight can be measured using a calibrated spring balance or Newton meter
• Resultant force


  The overall force acting on an object, found by adding forces in the same direction and subtracting forces in opposite directions
• Finding the resultant force of two forces not acting in the same plane

  1. Draw a scale diagram using a protractor

  2. Measure the length of the diagonal to find the size of the resultant force

  3. Measure the angle to find the direction of the resultant force
• Finding the components of a diagonal resultant force

  1. Draw a scale diagram

  2. Measure the horizontal and vertical components using the scale
• Newton's first law


  When the resultant force on an object is zero, its acceleration is zero (it remains at constant velocity)
• Newton's second law


  The acceleration of an object is proportional to the resultant force acting on it, and inversely proportional to its mass
• Newton's first law of motion

  1. Resultant force on an object is zero

  2. Acceleration is zero

  3. Object stays stationary or moves at constant speed
• Newton's second law of motion

  1. Acceleration of object is proportional to resultant force

  2. Acceleration is inversely proportional to mass of object
• Force


  Mass times acceleration
• Meters per second squared is one unit, the squared is part of the unit
• Acceleration is a vector, it can be negative to show slowing down
• Required practical: Acceleration


  1. Use air track and glider

  2. Glider attached to pulley with weight

  3. Light gates measure velocity

  4. Repeat with different forces
• Typical car mass is around 1000 kg, lorry mass is about 40 times heavier
• Work


  Force causes an object to move through a distance
• Deformation


  Changing the shape of an object due to more than one force acting on it
• Elastic objects


  • Return to original length/size when force removed
  • Have a limit of proportionality
• Inelastic objects


  • Can be permanently deformed, don't return to original size
• Elastic potential energy


  Energy stored in a stretched/compressed spring
• Hooke's law


  Force applied to a spring is proportional to its extension
• Hooke's law holds until the limit of proportionality is exceeded
• In Hooke's law practical, force is plotted on x-axis and extension on y-axis to find spring constant
• Distance


  Number of steps taken on a journey
• Displacement


  Number of steps to get back home directly
• Speed


  Scalar quantity, how fast an object is moving
• Velocity


  Vector quantity, speed in a particular direction
• Typical speeds: walking 1-2 m/s, running 3-5 m/s, cycling 5-10 m/s
• Acceleration


  Vector quantity, change in velocity over time
• Acceleration can be positive (speeding up) or negative (slowing down)
• Distance-time (DT) graph


  Horizontal line = stationary, diagonal line = constant speed, steeper line = faster speed