<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
Skip Navigation
You are viewing an older version of this Concept. Go to the latest version.

Universal Gas Law

The universal gas law relates temperature, pressure, volume and moles of a gas in a single equation.

Atoms Practice
Practice Now
Hot Air Balloons

Hot Air Balloons

Credit: Carolyn Conner
Source: http://www.flickr.com/photos/42966376@N02/4267826080/
License: CC BY-NC 3.0

One of the earliest forms of flight, hot air balloons demonstrate how beautiful and simple Newton's 2nd law and the principles of buoyancy can be.

News You Can Use

  • Newton's 2nd law states that the sum of all the forces acting on an object is equal to the mass of that object times its acceleration. Therefore, for a hot air balloon to life up in the air, the net force on it must be point upward. Using Newton's 2nd law

  •  is the buoyant force directed upward and  is the force due to gravity that is pointing vertically downward. The buoyant force, from Archimedes principle is

where  is the density,  is the displaced volume and  is gravity.

  • Credit: Hans
    Source: http://pixabay.com/en/balloon-hot-air-balloon-balloon-glow-8478/
    License: CC BY-NC 3.0

    The part of the aircraft that looks like a balloon is called an envelope [Figure2]


  • Since the air inside the hot air balloon is heated up by the burners, it is less dense than the surrounding cooler air outside the balloon. When enough lift is generated the buoyant force is greater than the weight of the balloon and occupants and the balloon begins to accelerate upwards.

Explore More

Using the information provided above, answer the following questions.

  1. Show mathematically what Newton's 2nd law says when the balloon's burners are heating up the air inside the balloon but there is no upward lift?
  2. What is the relationship between temperature and density?
  3. If the density of the air inside the balloon was greater than the density outside of the balloon, would lift be generated?

Image Attributions

  1. [1]^ Credit: Carolyn Conner; Source: http://www.flickr.com/photos/42966376@N02/4267826080/; License: CC BY-NC 3.0
  2. [2]^ Credit: Hans; Source: http://pixabay.com/en/balloon-hot-air-balloon-balloon-glow-8478/; License: CC BY-NC 3.0

Explore More

Sign in to explore more, including practice questions and solutions for Newton's First and Second Laws.
Please wait...
Please wait...

Original text