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# When I place a piece of paper on top of a book and drop it why does it hit the ground at the same time?

We did an experiment in physics class:

We first dropped a piece of paper and a book at the same time. The book hit first b/c the air resistance affected the paper more.

Then we placed the paper under the book and dropped it and they hit the ground at the same time

We then put the paper on top of the book and they both hit the ground at the same time when dropped.

Why did the last 2 experiments happen the way it did?

Reasoning you gave for when paper was on top of book seems so obvious, but I never thought of that! Fascinating

### 4 Answers

- 1 decade agoFavorite Answer
Because of gravity. ALL bodies on the surface of the earth accelerate towards it at the same rate 9.8m/s^2, ignoring air resistance, 9.8m/s^2 is the acceleration caused by earth's gravity on its surface. So if we drop two objects regardless of their weight they will hit the ground at the same time. In the case of the paper it falls slower because of air resistance. When the paper is at the bottom or top of the book air resistance is negligible so they fall at the same time.

When calculating the force of gravity between two bodies MASS does usually matter, the following is the Universal Law of Gravitation

Fg=(G * m1*m2)/r

Fg= gravitational force

m1= mass of one object

m2=mass of the other object

r = distance between objects

G= Universal gravitational constant

m1 would be the mass of the earth and m2 would be the mass of the paper or book, or any other object over the earth,r = the radius of the earth. The earth's mass is much more greater than any object on its surface and makes whatever mass we are talking about NEGLIGIBLE and the distance is constant, so the gravity on the earth's surface is basically constant and the same for all bodies, except when other forces are acting on the object in this case AIR RESISTANCE.

As we get further from the earth, r = distance from the earth gets larger and from the equation, you can see that the earth's gravitational force weakens as the distance between bodies increases, this happens in the case of satelites that are orbiting the earth, and scientists have to take this into account. So satelites actually experience a different force, a weaker one.

Another way you can test this if by crumpling your piece of paper into a ball as tight as you can, the paper has the same mass, drop a heavy book and the crumpled paper from the same height and they will hit the ground at pretty much the same time.

- Anonymous1 decade ago
aerodynamics plays a big part in that experiment when the paper is on the bottom of the book it acts like it is part of the book and will fall at the same time. and when the paper is on top of the book it falls at the same rate as the book because the wind resistance is negligible.

- kulpaLv 44 years ago
the formulation for weight is as follows: weight = mass * gravity. mass = finished kind of debris that make up the paper. gravity = the stress that acts on those debris. a paper has lesser mass( much less no of debris eg m = 10(debris) a e book has greater paper so greater mass( it has 5 pages: m = 10*5 = 50) as a result weight of paper weight = 10*g weight of e book = 50 *g heavier products consistently fall speedier, a stone falls speedier than a feather. that's the explanation. word: distinctive debris that make up distinctive products have distinctive hundreds. eg;- 10 debris of sponge has much less mass; than 10 debris of sand. as we are dealing basically with the same textile paper. its no longer a controversy for the published question