If you ask people around you, what will they say? Even you may be thinking the answer is YES, that heaver objects fall faster so If you drop a heavy and light object together, the heavy one will get to the ground first.
This is trick question because the is more factors than you may have considered that comes into play.
Even Physics students would hastily say NO, that they fall the same way. But physics tells us their is more to it.
Why would people say the first answer? Remember that essentially all
ideas are based on something. Even if they are wrong, they should make
some sort of sense otherwise we would just be crazy person. The idea
that a heavy object falls faster does seem to agree with our everyday
observations.
Try these experiments
- Take a baseball and a ping pong ball and drop them
together
It will probably be closer than you think but the heavier
baseball will indeed hit the ground first. Your initial thoughts would
be confirmed. Heavier things do indeed fall faster. But don't conclude yet till we concluded our experinments
- Here is the first classic example. Try a bowling ball and a basketball dropped from the same height.
These two objects clearly have different mass but they fall with the
same acceleration. I guess I should point out one more thing about
falling objects. If you were to measure the position of these balls as
they fall, they do not fall with a constant speed. Instead, they fall
with a constant acceleration. That is to say that as they fall, the
speed increases. For these two objects, they hit the ground at the same
time because they both start from rest and both have the same
acceleration.
Here is another example that you can try yourself.
- Take two sheets of
plain paper. They have the same mass, right? Now crumple one up into a
ball and then drop both.
Even though they have the same mass, the
crumpled one will hit the ground first.
Here is a better example.
- Have a crumpled up piece of
paper and some type of foam board.
The paper has a mass of 5 grams and
the board is 240 grams. Just as a hint, that’s a big difference in mass.
But which one hit the ground first? Yup, the piece of paper. Awesome,
right? And then when I turn the foam board so that the thin side faces
down, BOOM. They both hit the ground at the same time.
So, what hits the ground first?
Everything. Above you can see it all.
Both heavier and lighter things can fall faster. Clearly, you can’t
just say “heavier is faster”.
SIMPLE FACTORS THAT DECIDES WHICH SHOULD LAND FIRST
Acceleration of Falling Objects
Let’s look at the case of a falling bowling ball and basket ball. This is a force diagram showing the two objects.
The bowling ball has a greater mass so it also has a greater
gravitational force. You can calculate this gravitational force as the
product of the mass (m) and the gravitational field (g). There is
something else that depends on the mass, the acceleration. If there is
only one force on an object then the following would be true (in one
dimension):
Since both the acceleration AND the only force depend on mass, I can write:
Heavier things have a greater gravitational force AND heavier things
have a THE SAME acceleration as lighter objects due to the effect of the greater mass that the gravitational force have to pull . It turns out that these two effects exactly
cancel to make falling objects have the same acceleration regardless of
mass.
Air Resistance
Clearly, I didn’t fully address all the issues above. If all objects
have the same falling acceleration, then why did the crumpled up paper
hit the ground before the foam board? The problem is that I left off a
force – the air resistance force.
Here’s another experiment. Put your hand out the window of a moving
car. What do you feel? You can feel the air pushing against your hand.
If the car drives faster, the air resistance force gets larger. If you
make your hand into a fist instead of an open hand, the force decreases
.
This air resistance force is really just the sum of the tiny impacts
with your hand and the air. It depends on the air speed as well as the
size of the object.
Then what happens as you drop both a foam board and a crumpled piece
of paper? At first, they have the same acceleration since they both have
a zero velocity which makes zero air resistance force. However, after
some short time the forces might look like this:
The foam board has a larger gravitational force but it also has a
very large air resistance force. The net (total) force on the foam board
will give it a smaller acceleration than paper.
But what about the basketball and the bowling ball? Shouldn’t they
have different accelerations? Technically, yes. Let me redraw the force
diagrams for these two objects and include air resistance.
For these objects, the gravitational force is huge in comparison to
the air resistance force. Essentially, it doesn’t do much to change the
falling acceleration of these objects. But when does it matter? This is a
tough question. First, anything at a very low speed will have a mostly
negligible air resistance and at high speed will have significant air
resistance. Here are some cases where you would NOT ignore air
resistance:
- A falling piece of paper or a feather.
- A falling human at high speeds (a sky diver).
- A professionally thrown baseball (100 mph).
- A ping pong ball.
- Tiny rocks or gravy.
I know that doesn’t fully answer the question about air resistance,
but it gives you an idea of where to start. But it turns out that there
are many situations where a heavier object does indeed hit the ground
before a lighter object (because of air resistance). I guess this is
why Aristotle and many others think this is always true
Reference source :
www.wired.com
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