motive power

It said it had received 95 complaints alleging that the oil pump may fail, resulting in a loss of motive power while the vehicle is in motion.

I provide the motive power, a.k.a. the push.

The stationary earth cannot be the source of that motive power, so the innermost sphere must be moved by the next sphere out.

“A clever man will never underestimate the motive power of dust and bones,” O’Connor contends.

"The ship will simply be hoisted up and will ride safely and firmly…the current will be our motive power, while our ship, no longer a means of transport, will become a barrack."