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 Fall Line and Gravity in Skiing
Name: Mel F.
Status: other
Age: 60s
Location: N/A
Country: N/A
Date: 5/22/2003


Question:
Perhaps you can clear my confusion. In alpine skiing, the "fall line" is defined as the path water would take when flowing down an incline. A skier turns into the fall line to go down the hill. The Professional Ski Instructors of America have changed this terminology to the line of gravity, as "turning into or turning out of the line of gravity". I believe this to be incorrect, as gravity pulls toward the center of the earth, not down an incline. Am I right? I believe I qualify as a student as I am studying for my level 1 certification with P.S.I.A.


Replies:
Yes, gravity pulls objects down toward the center of the earth, and that is the normal component, or downward force that is always pulling on you. When you are on an incline, the pull of gravity now has an angular component to the force pulling you down the hill due to the path of the incline. Instead of it being the full blown gravity if you were to free fall, you have a smaller amount of force pulling you down the hill, but it is still due to gravity. The "turning into or out of the line of gravity" is just a way of saying that you are going to affect the pull of gravity on your body by changing the angular gravity component. One way to think of this is a ball rolling down an incline. The steeper the incline the faster the ball rolls down the incline. It is no different than you skiing down a hill. If you don't push off on the skis, gravity is the only force taking you down the hill.

If you know a little something about vectors, it may help you to understand how gravity and the direction of your skis influence your trip down the mountain. If you still have questions, write us back and ask about the vector component of skiing downhill.

Regards,

Chris Murphy



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