Sideways Icicles

Icicles on a roof growing sideways because of prevailing wind currents demonstrates that the applied wind force partially overcomes the gravitational force downward.
 

Possible Guiding, Compelling and/or Anchoring Questions

• What forces are involved?
• How long were the forces affecting the icicles? 
• Why did the phenomenon occur here but not elsewhere?

Classroom Suggestions

• Topics: Forces in Two Dimensions, Addition of Vectors
• Show the photo of the icicles and have students generate questions about them. 
• Enlarge the phenomenon photo and zoom in on the icicles for a closer look or to measure angles.
• To focus on forces, use the Sideways Icicles Video clip showing the wind pattern on the building. 
• Additional photos: Ice formations on trees in wind  photographed by Marko Korosec: Extreme conditions of humidity, freezing temperatures, and high wind created ice formations that are nearly horizontal. 

Related Resources

• How Are Icicles Formed: This article explains the process of icicle formation and ties it to stalactites in caves.
• Kinematics in Two Dimensions: An Introduction: This lesson explains how motion can be described as made up of vertical and horizontal components. It also features links to other resources, and is suitable for teacher background or a physics class.
• The Physics Classroom: Addition of Forces: This article explains the process of adding vectors to find the net force. It also features links to other resources, and is suitable for teacher background or a physics class.
• The Physics Classroom : Vector Addition Interactive: This lesson contains teaching notes and a link to an interactive to help teach addition of vectors. Students can insert the vectors involved and it will give the resultant magnitude and angle.