Physics 6.2

• Newton's Laws created


  1687
• Mass


  The amount of matter in an object, measured in kilograms (kg), does not change regardless of the environment
• Weight


  The force of gravity on an object's mass
• Gravity


  A force that attracts mass together
• Inertia


  An object's mass is also a measure of how difficult it is to change the object's motion. An object with high mass has more inertia than an object with lower mass.
• Force


  Another name for acceleration, the force that has an attraction to the earth's mass and the mass of an object, measured in newtons
• Force (F)


  Equals mass (m) times acceleration (a), F=ma
• On Earth, the gravitational field strength is 9.8 N/kg, meaning the mass of the earth attracts every 1kg mass with a weight force of 9.8N</b>
• On the moon, the gravitational field strength is 1.6 N/kg
• Newton's First Law


  • An object at rest will remain at rest unless an unbalanced force acts upon it. An object in motion will remain in motion with the same speed and direction, unless acted upon by an unbalanced force.
• Newton's Second Law


  • Acceleration is produced when a force acts on a mass. The greater the mass, the greater the force needed to accelerate the object.
• Resultant force acting on an object

  Causes the object to change velocity in the direction of the resultant force, which could be acceleration, deceleration or change in direction
• Newton's Third Law


  • For every action, there is an equal and opposite reaction. If body A exerts a force on body B, B exerts an equal and opposite force on A.
• Momentum


  Describes how much kinetic energy an object is transferring, calculated as mass x velocity (p=mv)
• Change in momentum over time


  Equals force (Δp/Δt = F)
• Types of forces


  • Gravity
  • Thrust
  • Friction/Air resistance
  • Reaction
• Terminal speed/velocity


  The speed at which the force of air resistance/drag becomes equal to the force of gravity, resulting in a constant speed
• Skydiver reaching terminal velocity

  1. Gravity pulls the skydiver down

  2. Air resistance increases

  3. Resultant force decreases

  4. Gravity and air resistance become equal

  5. Skydiver reaches terminal velocity
• Passenger in a car during acceleration

  Thrown backwards due to resultant force in forward direction
• Passenger in a car at constant speed


  Remains where they are as there is no resultant force
• Passenger in a car during deceleration


  Thrown forwards due to resultant force in backwards direction
• Air resistance is a frictional force opposite to gravity or thrust
• Car accelerating


  Air resistance increases until forces are equal, then car travels at terminal velocity