Friday, 10-15

Today we explored Air Resistance: force that acts to oppose an object's motion as it moves through the air (or any fluid can resist...)
Depends on:
Density of fluid
Speed of object relative to fluid
Shape of object
Size of object

Demonstration: air resistance in a vacuum: We pumped most of the air from a cylinder and found that a feather drops at the same rate as anything else (like a BB) without air resistance.

Logic problem: We also analyzed a skydiver's motion as they fall from a stop (right after exiting a plane, etc) to when they reach terminal velocity. Acceleration is highest at the start and decreases to zero when they reach maximum speed.

After that we went over the homework from last night and watched videos involving air resistance - a bicycle that goes over 80 mph, new cars' technology for aerodynamics and economy, and guys using wing suits to increase air resistance when base jumping... giving them a lower terminal velocity and allowing them to do some amazing stunts.

A note of caution: Don't confuse the terms velocity and acceleration.
Acceleration is negative when an object's velocity decreases.
Acceleration is not necessarily decreasing when an object's velocity decreases. If you're asked to describe acceleration of an object speeding up, you should answer "positive acceleration", not "increasing acceleration" The acceleration might be absolutely constant, or decreasing, but if it's at all positive, the item involved is speeding up.