Force

Forces and Motion

## When the sum of the forces is zero

Teaching Guidance for 14-16

#### 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.