Newton's laws of motion: Forces: Physics: GCSE (9:1)

• Newton's First Law

  An object remains in the same state of motion unless a resultant force acts on it
• Resultant force


  A single force that has the same effect as the original forces on an object acting together

  
• When the resultant force is zero

  A stationary object stays stationary and moving object continues to move at the same speed and in the same direction

  
• Newton's Second Law

  The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object

  
• F = ma

  The equation linking resultant force, mass and acceleration

  
• F


  The symbol for force

  
• m


  The symbol for mass

  
• a


  The symbol for acceleration

  
• Newtons (N)


  The SI unit for force

  
• Kilograms (kg)


  The SI unit for mass

  
• Metres per second squared (m/s²)


  The SI unit for acceleration
• Newton's Third Law

  Whenever two objects interact, the forces they exert on each other are equal and opposite

  
• (higher-tier only)

  Inertia


  The tendency of an object to continue in their state of rest or of in uniform motion (not accelerating)
• (higher tier-only)

  Inertial mass

  A measure of how difficult it is to change the velocity of an object or the ratio of force over acceleration