3 ms·

Same question. The balance wheel/hairspring has to be losing energy overtime to friction (however miniscule). Otherwise we have ourselves a perpetual motion mac

• panki27 4y ago
  This is mentioned in the article. The pallet fork gives the balance wheel a small push after unlocking, giving it a tiny bit of extra momentum.
• alfalfasprout 4y ago
  To add to the other answer, that friction (and the intertia of the balance wheel) is actually factored in when regulating the watch. The pallet fork gives the balance wheel a nudge on every "Tick" then the pallet fork stays stuck until the balance wheel swings around and back and jolts it in the other direction (the tock). Basically a little bit of energy is released from the mainspring via the escapement to the pallet fork to the balance wheel on each tick/tock.