FORCES

Forces and Their Effects – Remember it!

Forces and Their Effects – Remember it!

force

  • – An object can have one or more forces acting on it at the same time.
  • – The sum of these forces is called the resultant force.
  • – A resultant force is zero when all the forces are balanced.
  • – If the forces aren’t balanced then the resultant force is not zero. An object will then move as dictated by the force.
  • – An object accelerates only when the resultant force isn’t zero.
  • a = F / m
  • – The distance it takes for a vehicle to stop depends the thinking distance and the braking distance.
  • – When a vehicle is travelling at a steady speed the resultant force is zero.
  • – The driving force from the engine is balanced by a number of resistive forces including air resistance.
  • – When a vehicle speeds up the force of gravity and the reaction force coming from the road stay balanced and the driving force becomes greater than the resistive forces.
  • – When a vehicle slows down either the resistive forces need to increase and/or the driving force coming from the engine needs to be reduced.
  • stopping distance = thinking distance + braking distance
  • Physics GCSE science revision- ForcesThe thinking distance increases with the speed at which the vehicle is travelling. It also increases as the reaction time increases.
  • – The reaction time can be affected by a number of factors.
  • – The braking distance is the distance it takes a vehicle to stop once the brakes have been applied.
  • – The speed at which at object falls is affected by its weight and air resistance.
  • – Once an object is falling at a steady speed it’s reached its terminal velocity.
  • – Mass is the amount of stuff contained within an object.
  • – Weight is a force which acts on the stuff.
  • W = m x g
  • – If an object is falling to Earth: W = m x a
  • – An elastic object is able to store energy as elastic potential energy.
  • – Hooke’s Law states that the extension of an elastic object and the force applied to it are directly proportional to one another.
  • – Hooke’s Law is only correct if the elastic limit, which is the limit of proportionality, is not exceeded.