| NATS 101 Lecture 16 NewtonÕs Laws of Motion Upper-Air Winds |
| Supplemental References for TodayÕs Lecture |
| Gedzelman, S. D., 1980: The Science and Wonders of the Atmosphere. 535 pp. John-Wiley & Sons. (ISBN 0-471-02972-6) | |
| Slide 3 |
| Do Rocks Always Roll Downhill? |
| NewtonÕs Laws of Motion |
| NewtonÕs 1st Law | |
| An object at rest will remain at rest and an object in motion will remain at a constant velocity (same speed and same direction) if the net force exerted on it is zero | |
| An external force is required to speed up, slow down, or change the direction of air |
| NewtonÕs Laws of Motion |
| NewtonÕs 2nd Law | |
| The net force exerted on an object equals its mass times its acceleration | |
| Sum of All Forces = Mass « Acceleration | |
| Acceleration = Velocity Change / Time | |
| Acceleration = Change in Either Speed or Direction |
| Velocity, Acceleration and Force are Vectors |
| Size and Direction | |
| Uniform, Circular Motion Requires Acceleration |
| Accelerated Frame of Reference |
| You are glued to carÕs floor and drop an egg. | |
| What happens if the car begins to accelerate? |
| Life on a Rotating Platform |
| From perspective of person not on merry-go-round, path of ball is straight. | |
| From perspective of person on merry-go-round, path of ball deflects to left. There is an apparent force. |
| EarthÕs Rotation |
| Ball Appears to Deflect to the Right of the Observer |
| Ball Appears to Go Straight |
| Deflection Depends on Orientation of Axis of Rotation and Velocity |
| Coriolis Force Varies with Latitude |
| Geostrophic Adjustment |
| Parcel at rest initially accelerates toward lower pressure. | |
| Coriolis Force rotates parcel to right in NH. | |
| As parcel speeds up, Coriolis Force increases. | |
| Eventually (about a day), PGF equals CF and flow is parallel to isobars. |
| Geostrophic Balance |
| Geostrophic Balance |
| Slide 19 |
| Do Rocks Always Roll Downhill? |
| Key Concepts for Today |
| Rotation of Earth | |
| Accelerated Frame of Reference | |
| Introduce Coriolis ÒForceÓ | |
| Apparent Force to Account for Deflection Depends on Rotation, Latitude, Wind Speed | |
| Geostrophic Balance and Wind | |
| Balance Between PGF and Coriolis Force Geostrophic Wind Blows Parallel to Contours About One Day Required to Reach Balance |
| Assignment for Next Lecture |
| Topic – Centripetal force due to curved flow | |
| Frictional force near the ground | |
| Reading - Ahrens pg 155-158 | |
| Problems - 6.23, 24 (24,25) | |