Unbalanced or Resultant?

  • An object will remain stationary or continue to move at a steady speed in a straight line unless there is an unbalanced force.
  • An object will remain stationary or continue to move at a steady speed in a straight line unless an unbalanced force acts on it.
  • An object will remain stationary or continue to move at a steady speed in a straight line unless there is a resultant force acting on it.
  • An object will remain stationary or maintain a constant velocity unless there is a resultant force acting on it.
  • The velocity of a body will not change unless there is a resultant force acting on it.

All these statements of Newton’s 1st Law are correct; which is best for GCSE teaching? Should we consistently use ‘resultant’ or use ‘unbalanced’ sometimes to emphasise the idea behind it? Should we always break down ‘changing velocity’ to emphasise that ‘starting moving’, and ‘changing direction’, are counted or should we work until the students never respond as if velocity just means speed, and then always use velocity? And if so, should we insist on practising until they reach that point before we do Newton 1? Any thoughts – I have a view but I’m available for conversion.

There is a lot of emphasis at the moment on using the correct scientific language. I am in general agreement with this e.g. calling a liquid ‘viscous’ instead of thick is the example from the Durrington High School blog but is there a point where the need to shift misconceptions trumps the need to teach the formal language of our subjects?

And what is the adjective to describe water if the adjective to describe glycerol is ‘viscous’?

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