Every earlier motor step lesson in this book (chapters five and six) fixed step length at 2 m and only ever scanned force or step count. This scan holds force (6 N) and step count (one) fixed and checks three step lengths instead: 1 m gives per-step work 6 J, 2 m reproduces chapters five and six's own checked step length exactly at 12 J, and 3 m gives 18 J. Step length is the third independent factor in motor step work, and it had never been scanned on its own.
Every earlier motor step lesson fixed step length at two metres and scanned force or step count; this scan holds those fixed and scans step length itself. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Every earlier motor step held step length fixed at two
Chapters five and six both kept step length at 2 metres and only ever varied force or step count. Here force stays 6 newtons and step count stays one, but step length itself shortens to 1 metre, giving per-step work 6 joules.
6⋅1=6
Step length itself decides how much a fixed force buys
Force and step count never change across these rows. Step length alone rescales the checked work-per-step arrow.
6⋅2=12
A longer step buys more work from the same force
At step length 3 metres, the same force gives per-step work 18 joules. Three rows separate step length from the force and step-count factors already scanned in chapters five and six.