Forces and Motion

When the sum of the forces is zero

Teaching Guidance for 14-16 Supporting Physics Teaching

Said, and best left unsaid

Teacher Tip: We'd suggest using the phrase the forces add to zero as a step on the way to saying the resultant force is zero, and definitely avoiding the forces cancel out.

There are two main reasons for suggesting this:

  • Adding the forces and finding that the resultant is zero is exactly what you do.
  • The process of cancelling might evoke memories of dealing with ratios or fractions. That's not appropriate for vectors – there are no good mathematical rules for performing these operations with vectors.
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