Paper 2

• What is a force?

  A force is a push or pull that can cause an object to move, stop, or change direction.
• Scalar vs Vector

  Scalar: Physical quantities that include magnitude and unit. E.g Mass or energy

  Vector: Physical quantities that include magnitude, direction and unit. E.g Weight or Force
• Distance vs Displacement

  Distance: Total journey covered

  Displacement: Links initial and final points of journey
• Human error happens when people make mistakes
• Human error happens even when measuring is done correctly if an investigation is not carried out in the right way
• Types of errors

  • Random errors
  • Systematic errors
• Random errors

  There is no pattern to the errors, happens when repeated parts of an investigation are not done in exactly the same way, measurements are not precise
• Systematic errors

  Repeated parts of an investigation are done in the same way but that way is not correct, measurements are precise but not accurate
• Levers can move objects by turning them around a pivot
• Turning effect caused by a force

  Moment of a force
• Moments

  Measured in Newton metres, Nm
• The larger the moment, the greater the turning effect
• Centre of gravity

  The point that the weight acts through
• Centre of mass


  The entire mass of an object that can be treated as thought it acts as a single point
• What Is a gear?

  A gear is a mechanical component with teeth that mesh with another gear to transmit motion or power.

  These are used to transmit ROTATIONAL FORCES
• Types of gears:

  Driver, idler and follower gears
• Pressure in a liquid

  Will increase in depth

  > The water at the bottom the container is pushed on by the weight of the water above it, causing for higher pressure
• Air pressure

  The pressure exerted by the weight of air on the Earth's surface
• How air pressure changes with height

  1. As you increase height above sea level

  2. The air pressure decreases
• Reason for decrease in air pressure with height

  • There are fewer air particles for every cubic meter of air
  • Fewer particles hitting you means there is less pressure
• Photo taken at height

  • 2415m
• The air exerts pressure on the surfaces on earth
• Atmospheric pressure

  About 100 000pa (1 bar), although this varies around the world and day to day
• Cause of atmospheric pressure

  • The pressure is caused by the air particles (a gas) hitting surfaces
  • As there are so many air particles this is constant
• Newton's First Law


  Deals with objects at rest (v=0) or those moving at a constant speed
• Newton's First Law


  If no resultant force acts, an object will remain stationary or move with a constant speed in a straight line
• Inertia


  The tendency of objects to continue in their state of rest or of uniform motion
• Newton's Second Law


  • Deals with the relationship between force, mass and acceleration
  • When a resultant force acts on an object, it produces acceleration/deceleration
  • The larger the force, the larger the acceleration
  • The larger the mass, the smaller the acceleration
• Newton's Second Law


  F = m x a
• Resultant force, acceleration, and mass are related by the equation F = m x a
• Stopping distance = braking + thinking distance
• What is momentum?


  A measure of how difficult it is to stop a moving object
• Momentum (p) = mass (m) x velocity (v)