Understanding Newton's Third Law: The Cause of Balloon Movement

In summary, the force that causes a balloon to move in the opposite direction when filled with air is thrust, which is a result of the elastic force of the balloon trying to compress back to its original shape. This force is a form of conservation of momentum, similar to the force that propels rockets into orbit. The air inside the balloon exerts pressure on the balloon's inner surface, but since there is a hole for the air to escape, the force is mostly exerted on the opposite side of the hole.
  • #1
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If you fill a balloon with air and let it go, since the initial momentum was 0 and the air in the balloon is pushed in one direction, the balloon must move in the other direction. What is the cause of the force that causes the balloon to move this way?
 
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  • #2
The force that causes the balloon to move the other way is thrust, the same force pushing rockets into orbit. The particular thrust here comes ultimately from the elastic force of the balloon trying to compress back to its original shape, but having to work against the pressure of the gas inside.

Thrust itself comes from conservation of momentum.
If you throw something away from you (for the balloon, this would be a stream of air), you experience a kickback force (i.e., thrust), because the total momentum of you plus the thrown object must add up to the same value before and after the throwing event (assuming no other external forces).
 
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  • #3
I'd say that the air in the balloon pushes on the inside surface of the balloon, but the balloon skin is missing at the hole through which the air escapes, so the push on the inside of the balloon is more on the side opposite the hole.
 
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Related to Understanding Newton's Third Law: The Cause of Balloon Movement

1. What is Newton's Third Law and how does it apply to balloon movement?

Newton's Third Law states that for every action, there is an equal and opposite reaction. In the case of balloon movement, when air is forced out of the balloon, it exerts a force in the opposite direction, causing the balloon to move forward.

2. Why does a balloon move in the opposite direction of the air being released?

This is due to Newton's Third Law. As the air is released from the balloon, it pushes against the surrounding air, creating an equal and opposite reaction that propels the balloon forward.

3. How does the size or shape of a balloon affect its movement?

The size or shape of a balloon can affect its movement because it can impact the amount of air being released and the direction of the force. A larger balloon will typically release more air, resulting in a stronger force and a faster movement. The shape of the balloon can also affect the direction of the force, causing the balloon to move in a different direction.

4. Can Newton's Third Law be applied to other objects besides balloons?

Yes, Newton's Third Law applies to all objects and their movement. Any time there is an action, there will be an equal and opposite reaction. For example, when a person walks, their feet push against the ground and the ground pushes back, propelling them forward.

5. Are there any real-life applications of understanding Newton's Third Law in relation to balloon movement?

Yes, understanding Newton's Third Law in relation to balloon movement has real-life applications in various fields such as aerospace engineering, where it is used to design and control the movement of aircrafts. It is also used in sports, such as in the propulsion of rockets and in the physics of throwing a ball.

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