2.4 physics

• Momentum


  Moving objects have momentum, which means it is likely to continue travelling in the direction it is current heading in. The greater an object's momentum, the harder it is to change its direction. Momentum depends on velocity and mass.
• Newton's 2nd Law


  Resultant forces and acceleration of an object are related (F=ma). This law can also be used with the concept of momentum. The force experienced is related to the change in momentum over time.
• The faster the momentum is changed, the greater the force experienced as the time over which the momentum change takes place has been reduced
• Conservation of Momentum


  In a closed system, where no external forces act, the total momentum before and after an event remains the same. This includes explosions and collisions. Momentum is conserved.
• Newton's 3rd Law


  Every action has an equal and opposite reaction. Momentum and kinetic energy can be considered in the same way and can indicate the type of collision occurring.
• Elastic Collisions


  In an elastic collision, kinetic energy is conserved so kinetic energy before equals kinetic energy after. Interactions between molecules on an atomic level are elastic, meaning kinetic energy is conserved.
• Inelastic Collisions


  Most collisions in the natural world are not perfectly elastic meaning some energy is converted to other forms, so kinetic energy is not conserved. These collisions are described as inelastic. Momentum is conserved and energy is conserved, but kinetic energy is not.
• SUVAT Equations


  The movement of objects can be quantified and related through a set of equations known as the SUVAT equations.
• Moment


  The turning effect of a force around a fixed pivot point. The size of a moment (M) depends on the force applied and the perpendicular distance of the applied force from the pivot point.
• Moments help to understand why it is easier to do things like open a door at the handle rather than at the hinge. Increased distance from the hinge (pivot) means less force is required to unlock the door. This is because the moment is greater the further from the pivot a force is applied.
• Balancing Moments


  If multiple moments are acting at once, the total moment in that direction is the sum of the separate moments. Moments are vectors, so the direction they act in is important to consider.