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Aristotle · Mechanics §31.1-31.2

Why Moving Objects Are Easier to Move Than Resting Ones

Passage 34 of 38 · Greek

Summary

This section explains why it is easier to move an object already in motion than one at rest, referencing the effects of resistance and the assistance of forward motion.

§31.1Διὰ τί ῥᾷον κινεῖται τὸ κινούμενον ἢ τὸ μένον, οἶον τὰς ἁμάξας θᾶττον κινουμένας ὑπάγουσιν ἢ ἀρχομένας;
Why is it that a thing in motion is moved more easily than one at rest; for instance, they draw carriages more easily when they are already moving faster than when they are starting?
Ἣ ὅτι χαλεπώτατον μὲν τὸ εἰς τοὐναντίον κινούμενον κινῆσαι βάρος;
Or is it because it is most difficult to move a heavy object that is moving in the opposite direction?
ἀφαιρεῖται γάρ τι τῆς τοῦ κινοῦντος δυνάμεως, κἂν πολὺ θᾶττον ᾖ· ἀνάγκη γὰρ βραδυτέραν γίνεσθαι τὴν ὦσιν τοῦ ἀντωθουμένου.
For some of the power of the mover is taken away, even if it is moving much faster; for it is necessary that the push becomes slower because of that which pushes back in return.
§31.2Δεύτερον δέ, ἐὰν ἠρεμῇ· ἀντιτείνει γὰρ καὶ τὸ ἠρεμοῦν.
Secondly, if it is at rest; for that which is at rest also offers resistance.
Τὸ δὲ κινούμενον ἐπὶ τὸ αὐτὸ τῷ ὠθοῦντι ὅμοιον ποιεῖ ὥσπερ ἄν εἰ αὐξήσειέ τις τὴν τοῦ κινοῦντος δύναμιν καὶ ταχυτῆτα· ὃ γὰρ ὑπ’ ἐκείνου ἂν ἔπασχε, τοῦτο αὐτὸ ποιεῖ εἰς τὸ πρὸ ὁδοῦ κινούμενον.
But that which is already moving in the same direction as the pusher produces an effect similar to what would happen if someone increased the power and speed of the mover; for that which it would have experienced from the mover, it does this very thing for itself in moving forward on its way.

Notes

  1. §31.1ὑπάγουσιν — A third-person plural verb with an indefinite subject ("people"). It takes τὰς ἁμάξας ("carriages") as its object, meaning "they draw/lead the carriages forward."
  2. §31.1κἂν πολὺ θᾶττον ᾖ — κἂν is a contraction of καὶ ἐάν ("even if"). The subject of the subjunctive ᾖ is the "heavy object moving in the opposite direction" (τὸ εἰς τοὐναντίον κινούμενον βάρος) from the preceding clause, meaning "even if it is moving much faster [in the opposite direction]."
  3. §31.1τοῦ ἀντωθουμένου — Genitive of the middle-passive participle of ἀντωθέω ("to push in return / push back"). It modifies ὦσιν ("push/thrust"), indicating the cause of the slowing down: "by that which pushes back in return."
  4. §31.2εἰς τὸ πρὸ ὁδοῦ κινούμενον — πρὸ ὁδοῦ is an adverbial idiom meaning "forward" or "on the way." It modifies the articular neuter participle τὸ κινούμενον ("that which is moving" or "the motion"), meaning "in the motion that goes forward."

Cite this passage

Aristotle, Mechanics §31.1-31.2. Humanitext Reader, https://reader.humanitext.ai/en/text/urn:cts:greekLit:tlg0086.tlg023.humanitext-grc1:31.1-31.2

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