Physics Van 3-site Navigational Menu

Physics Van Navigational Menu

Q & A: friction and falling rates

Learn more physics!

Most recent answer: 06/30/2018
Q:
I dont believe the statement that a rock and a feather would reach the ground at the same time provided there is no air friction when you are stating that the rock arrives sooner because the feather is subject to more friction. Get a ball of iron, say a 1 meter diameter, and build an identical ball but made of feathers, inside and in the surface, well round like, therefore the friction would be thes same for both, Are you telling me they would both arrive at the same time?
- Aleks (age 55)
Estonia
A:

For a given downward velocity the frictional force for those two balls would be equal, as you say. Since the feather-filled ball has less mass, that friction gives a bigger upward acceleration force on the feather ball. Ths the net downward acceleration is lower for the feather ball. If there were no friction, both balls would just accelerate at rate g downward.

Mike W.

Evidence that this is true was privided by an astronaught on the moon in 1971.  See https://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_15_feather_drop.html


(published on 06/30/2018)

Follow-up on this answer.