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This question already has an answer here:

If I dropped book and feather from same height. Why book falls first, however book has more windage(air resistance), more area(square) than feather?

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marked as duplicate by Qmechanic May 3 at 16:51

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The book may have a larger drag force (although that also depends on shape, so it's not necessarily the case), so there is a larger total force trying to slow it down. But at the same time, it also resists this force much better due to its large mass. The feather, on the other hand, is very sensitive to even small forces appearing.

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  • $\begingroup$ What does it mean for the book to "resist" a force? Are you talking about inertia? $\endgroup$ – Will May 4 at 13:05
  • $\begingroup$ @Will Yes, inertia. $\endgroup$ – Steeven May 4 at 13:07
  • $\begingroup$ could you explain in a bit more detail why inertia is the pertinent phenomenon in this situation? $\endgroup$ – Will May 4 at 13:19
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Because of the mass. The more massive objects have a higher terminal velocity. This can be seen by equating the drag force with the gravitational force

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The acceleration due to gravity is the same for all bodies , large mass or small mass.

In a vacuum, a bowling ball and a feather fall at the same time , as demonstrated in this video.

The buoyancy due to the existence of air is different for a feather or for a ball or for a book. A helium filled balloon rises, instead of falling.

So it is a combination of the force of gravity pulling down, and the shape of the object and its resistance to the fall through the air. A book is smoother than a feather.

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The force of air resistance on the book may indeed be greater than the force of air resistance on the feather when they are moving at the same speed. But the force of gravity on the book is much greater on the book than on the feather. In order to find the terminal velocity (the speed at which either object falls), you find the speed at which the force of air resistance balances the force of gravity, which will be much higher for the book, since the book has higher mass.

In the accelerating regime (before reaching terminal velocity), a similar argument applies: the force of gravity is much larger on the book than on the feather, so the force of air resistance balances a much smaller proportion of the force of gravity on the book.

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