newton's laws

• balanced forces cancel each other out.

  unbalanced forces cause a resultant force to act on an object. for example:

  
• newton's first law:

  newton's first law states 'an object will remain at rest or at a constant velocity unless it is acted upon by an external resultant force'.

  
• difference between weight and mass:

  • weight is the force of gravity acting on an object
  • mass is the amount of matter in an object (mass does not change when you go into space but your weight will)
• weight= mass x gravitational field strength
• on earth the gravitational field strength is 10n/kg but this is different on other planets.
• if the forces are not balanced then the motion of the object will change.

  newton's second law can be used to calculate the acceleration or deceleration.

  
• resultant force= mass x acceleration
• newton's third law:

  newton's third law states that 'if a body A exerts a force on body B, then body B exerts an equal and opposite force on body A'.

  
• terminal speed:

  the forces acting on a sky diver as they fall are air resistance upwards and weight downwards. the sky divers weight remains the same throughout but the air resistance changes due to the changes in speed.

  
• terminal speeds can also be achieved with vehicles travelling horizontally, where air resistance and friction backwards increase to be equal to the engine's force forward.