forces & motion

• speed is the distance travelled over a period of time, measured in metres per second (= distance/time)
• velocity is speed in a certain direction (= final distance-initial distance/final time-initial time)
• Newton's first law of motion; an object will not change its motion unless a force acts on it
• Newton's second law of motion; the force experienced by an object is a product of its mass and its acceleration (F = ma)
• Newton's third law of motion; for every force, there is an equal and opposite force
• the four fundamental forces

  • gravity (force unit; newtons)
  • strong nuclear force (holds nucleus together)
  • weak nuclear force (within protons and neutrons)
  • electromagnetic force (includes friction, etc)
• electromagnetic forces;

  • tension & elasticity
  • friction
  • normal force
  • air drag
• a force is defined as; "a push or a pull or a twist"
• contact forces;

  • friction
  • air and water resistance
  • supporting structure
  • machines and muscles
• non-contact;

  • gravitational forces
  • electrostatic forces
  • magnetic forces
• the mass of an object remains constant, the weight of an object depends on gravity
• a force of one Newton will accelerate a mass of 1kg and at rate of 1m/s2
• for a given force, the greater the mass, the lower the acceleration & vice versa
• acceleration = force/mass
• deceleration is the slowing down of an object and the force acting on the object is acting in the opposite direction to its motion
• The Law of Conservation of Energy;Energy can be changed from one form to another, but it is never created, and never destroyed.
• • work is the amount of energy used to move an object (= f x d (force exerted in newtons x distance moved in metres)
• if an object moves when a force is applied, the energy change or work done is equal to the applied force multiplied by the distance moved (w = f x d)
• • power is the rate at which work is done (= energy change/time taken)