Paper 2

• kinetic energy is half the mass x the speed squared (1/2 mv^2)
• Unit for energy


  Joules (J)
• We use kg to measure mass
• Weight is measured in Newtons (N) and is the force acting on an object due to gravity
• Gpe formula


  mass x gravity x height
• Elastic potential energy is half of the spring constant x extension squared and is measured in joules
• Fast moving vehicles like cars and planes have a streamlinedshape to reduce friction from air resistance. This allows them to use less fuel
• Power is the rate at which energy is transferred, or the rate at which work is done
• Unit of power


  Watts (w)
• Power is work done divided by time taken to do work, or energy transferred divided by time taken to transfer energy
• How to reduce uncertainty

  Calculate a mean

  Use a larger sample
• Force


  Any push or pull
• Types of forces


  • Contact forces (when objects are physically touching)
  • Non-contact forces (like magnetism, electrostatic forces, gravity)
• Contact forces


  Normal contact force (pushing a door), friction, air resistance, tension
• Representing forces


  With vectors (arrows showing direction and magnitude)
• Resultant force


  The net force acting on an object when multiple forces are present
• Finding resultant force


  1. Technically adding the vectors, with forces in opposite directions being negative

  2. Using Pythagoras if forces are at right angles

  3. Using trigonometry (SOH CAH TOA) to find angles
• Balanced forces


  Forces that add up to zero, meaning the object will not accelerate
• Balanced forces mean the object stays at a constant velocity, which could be 0 m/s
• Scalar


  A quantity with magnitude but no direction
• Vector


  A quantity with both magnitude and direction
• Weight


  The force due to gravity acting on an object, calculated as mass * gravitational field strength
• Gravitational field strength on Earth is 9.8 N/kg, often rounded to 10 N/kg
• Lifting an object at constant speed


  Requires a force equal to the object's weight
• Calculating work done


  1. Work done = force * distance moved

  2. For lifting an object, work done = mass * gravitational field strength * height
• Hooke's law


  Force = spring constant * extension
• Spring constant


  The stiffness of a spring, measured in N/m
• The energy stored in a spring is equal to 1/2 * k * (extension)^2
• Moment


  A turning force, equal to force * perpendicular distance to pivot
• The unit for moment is newton-metres (N·m)
• Pressure


  Force per unit area, calculated as force / area
• Gas pressure


  Caused by collisions of gas particles with surfaces, increased by adding more gas, reducing volume, or increasing temperature
• Pressure decreases with increasing altitude due to lower atmospheric density
• Acceleration


  Rate of change of velocity, measured in m/s^2
• Calculating acceleration from a velocity-time graph

  Acceleration = gradient of the graph
• Calculating distance from a velocity-time graph


  Distance = area under the graph
• Newton's first law


  An object's motion is constant (including 0 m/s) unless acted on by a resultant force
• Inertia


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


  Resultant force = mass * acceleration
• Proving Newton's second law

  1. Use a trolley on a track, pulled by weights over a pulley, with light gates to measure acceleration

  2. Plot a graph of force vs acceleration, which should be a straight line through the origin