Every action has an equal and opposite reaction.

To decelerate the aircraft, the forward thrust of the aircraft which propels the aircraft forward is reversed by a Thrust Reverser. This is accomplished by redirecting all the air ( in small engines ) or partially ( in larger engines ) to the front.  

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Due to the flow of air to the front end of the aircraft, a reaction force acts in the opposite direction to the motion of the aircraft. This aids in the deceleration of the aircraft.

Hi! Just curious if you have any awesome perpetual motion machine ideas you could share 😊

Hey annavellichor, 

Perpetual motion machines… Wow! I haven’t had any productive design ideas for PMM’s at all. But I wish to share with you one of my favorites. It is highly efficient, but it eventually does succumb to nature.

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Friction! Thou art a heartless devil.

(Source: PMM- Youtube )