Skip to Content Go to sign in Skip to Primary Navigation Skip to Secondary Navigation Skip to Page Navigation Skip to Header Navigation Skip to Footer Navigation Read more about accessability options and our navigation

Physics Classroom is making strides to make our site accessible to everyone. Our site contains 6 navigation areas. The Primary, Secondary, and Page Level navigations have a screen reader version of their nav structure that allows using the left and right keys to navigate sibling navigation items, and up or down keys to navigate parent or child navigation items. The others can be navigated using tabs. The Primary Navigation handles the first 2 levels of site pages. The Secondary (which is not always available) handles the 3rd and 4th level of structure. The Page level navigation allows you to navigate the current page's headings quickly. The Header Navigation contains the Light/Dark Mode toggle, Search, Notifications and account login. The Breadcrumb Navigation contains the breadcrumb of the current page. If the current page has a breadcrumb, you can get to it by skipping to the content and tabbing in reverse (shift plus tab). The Footer Navigation contains links such as Privacy, Contact, about and terms. Some resources contain an Audio Player that can be activated by holding down the T key for 3 seconds, and then using K to pause and resume. While not every area of Physics Classroom is usable purely from keyboard and screen reader, we are committed to continue work on making this possible. If you have questions or need additional help, please use this link to contact us.

Return to screen reader navigation
Home Minds On Newton's Laws Mission NL11 Air Resistance Help Help 5

Mission NL11 Air Resistance

The Question

Suppose that an elephant and a feather are dropped from a skyscraper (just suppose). In the presence of air resistance, the elephant would fall faster than the feather because ...

Tune In! Listen!

Click the button below to play an audio file in a separate window.

Don't be Fooled

This question offers plenty of ways to be fooled, especially if you are careless with your physics terminology. So here's a quick language lesson:
 
  • First, the acceleration of gravity is the physics term that refers to the acceleration that all objects experience when in a state of free fall (acted upon by gravity alone). Since all objects free fall (no air resistance) at the same rate regardless of their mass, all objects have the same acceleration of gravity value.
  • Second, the mass of an object is the amount of stuff possessed by an object. An object with more stuff has more mass. (And that should help you evaluate the difference in mass between an elephant and a feather.) Mass is quite different than weight. Weight is the force of gravity that acts upon the stuff that an object possesses. Consistent with the formula Weight = m•g, objects with more mass have more weight.

Minds On Time

Air resistance is the upward force that resists the motion of a falling object. The amount of air resistance depends upon the speed of the falling object. As an object falls faster, the amount of air resistance increases. As the upward force of air resistance increases, it will eventually become equal in magnitude to the downward pull of gravity and a balance of forces exists. When this balance of forces exists, there is no more acceleration and the object is said to have reached a terminal or final velocity value. It will keep this velocity value for the remainder of the fall.
 
A feather, with its very small downward force of gravity, will reach this state of terminal velocity after a few moments of fall. Having very little weight, air resistance has a significant affect upon its motion. Very little air resistance is required to bring it to a terminal velocity. The elephant has a much greater downward force of gravity. An object as massive as an elephant will have to fall for a considerable time and reach high speeds before achieving a state of terminal velocity. Having such a large force of gravity, the affect of small forces of air resistance is almost insignificant. An elephant would have to fall for a long time, accelerating to high speeds before the air resistance force is large enough to balance the force of gravity. For this reason, a more massive elephant reaches greater terminal velocity values than a less massive feather.

Hot Link