Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Hot Air
Name: N/A
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: N/A


Question:
Why does hot air rise?



Replies:
Consider a small volume in air, we will assume that this volume contains hot air while the surrounding air is cold. The forces acting on this gas are - gravity acting downwards, pressure of gas acting upwards. Gravity is same for everything but acceleration caused by pressure depends on density. If this volume element is in pressure equilibrium with the surrounding gas, as it must be as the time taken to reach pressure eq. is generally very short, its density must be less than the surrounding gas. A less dense gas is accelerated faster and hence it rises in comparison with the surrounding cold air. For cold air the pressure neatly cancels the force due to gravity which gives us the stable atmosphere. As this packet of hot air rises, it expands to maintain pressure equilibrium with its surroundings and cools down.

jasjeet s bagla



Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory