Falling Object_Dana Santika_Physics Educational Department of Undiksha

7/31/2019 Falling Object_Dana Santika_Physics Educational Department of Undiksha

1/19

Elephant and Feather

Presented By

I Gede Dana Santika


2/19

Elephant and feather

Hi class, how are you?Im your physics teacher today.

Want to know my name?My name is .

Yach, I think you need to guess it!

Anybody knows?Nobody.

Well, my name isPUNSHUK WANGDU

Yach, call me Mr. Wangdu


3/19

Elephant and Feather

Hi,My name is Ranchoo.Im an elephant.My weight is 2 tons.

Glad to meet you.

Hi,My name is Catur.Im a feather.My weight is 2 grams.Bad to meet you.


4/19

Very High Building

The same highThe same time

No Air

Resistance

Who will hit the ground first?How can you explain me?

2 tons2 grams


5/19

No Air Resistance

Many people are surprised by the factthat in the absence of air resistance, theelephant and the feather strike theground at the same time.

But,Why is this so?

Take a look at the right animation!


6/19

Why is this so?

TRUE or FALSE

The elephant and the feather each have the same force of gravity.The elephant has more mass, yet both elephant and feather

experience the same force of gravity.The elephant experiences a greater force of gravity, yet both theelephant and the feather have the same mass.On earth, all objects (whether an elephant or a feather) have thesame force of gravity.The elephant weighs more than the feather, yet they each have the

same mass.The elephant clearly has more mass than the feather, yet they each

weigh the same.

The elephant clearly has more mass than the feather, yet the amountof gravity (force) is the same for each.

The elephant has the greatest acceleration, yet the amount ofgravity is the same for each.

If you answered TRUE to any of the question, then perhaps you havesome level of confusion concerning either the concepts or the words

force, weight, gravity, mass, andacceleration

No Air Resistance


7/19

In the absent of air resistance,

all object accelerates by thesame value, g.


8/19

In the absence of air resistance, both theelephant and the feather are in a state of free-

fall. That is to say, the only force acting upon thetwo objects is the force of gravity.

The force of gravity experienced by an object is dependentupon the mass of that object.

Now, Check this out!

Mass refers to the amount of matter in an object.Clearly, the elephant has more mass than the feather. Due to

its greater mass, the elephant also experiences a greaterforce of gravity.

That is, the Earth is pulling downwards upon the elephant withmore force than it pulls downward upon the feather.

Since weight is a measure of gravity's pull upon an object, itwould also be appropriate to say that the elephant weighs more

than the feather.

No Air Resistance


9/19

But if the elephant weighs more and experiences agreater downwards pull of gravity compared to the

feather, why then does it hit the ground at thesame time as the feather?

Great question!!

No Air Resistance


10/19

A simple rule to bear in mind is that all objects (regardless of their mass)

experience the same acceleration when in a state of free fall. Whenthe only force is gravity, the acceleration isthe same

value for all objects. On Earth, this acceleration value is 9.8 m/s/s.This is such an important value in physics that it is given a special name -

the acceleration of gravity - and a special symbol - g

But what about air resistance? Isn't itnonrealistic to ignore the influence of air

resistance upon the two object?

No Air Resistance


11/19

In the presence of air resistance, theelephant is sure to fall faster.

Is it right?Are you sure?Really?

Air Resistance

Yeah, you are definitely right.Congratulation!

ButWhy is this so?


12/19

Very High Building

The same highThe same time

Air Resistance

Who will hit the ground first?How can you explain me?

2 tons2 grams


13/19

Air Resistance

Most people are not surprised by the factthat the elephant strikes the groundbefore the feather.

But why does the elephantfall faster?

Take a look at the right animation!


14/19

TRUE or FALSE

Air Resistance

1. The elephant encounters a smaller force of airresistance than the feather and therefore falls faster.

2. The elephant has a greater acceleration of gravity thanthe feather and therefore falls faster.

3. Both elephant and feather have the same force ofgravity, yet the acceleration of gravity is greatest forthe elephant.

1. Both elephant and feather have the same force ofgravity, yet the feather experiences a greater airresistance.

2. Each object experiences the same amount of airresistance, yet the elephant experiences the greatestforce of gravity.

3. Each object experiences the same amount of airresistance, yet the feather experiences the greatestforce of gravity.

1. The feather weighs more than the elephant, andtherefore will not accelerate as rapidly as the elephant.

2. Both elephant and feather weigh the same amount, yet

the greater mass of the feather leads to a smalleracceleration.

3. The elephant experiences less air resistance and thanthe feather and thus reaches a larger terminal velocity.

4. The feather experiences more air resistance than theelephant and thus reaches a smaller terminal velocity.

5. The elephant and the feather encounter the sameamount of air resistance, yet the elephant has a greaterterminal velocity.

If you answered TRUE to any of the questions, then perhaps you

have some confusion about either the concepts of weight,force of gravity, acceleration of gravity, air

resistance and terminal velocity.


15/19

But why then does the elephant, which encounters moreair resistance than the feather, fall faster? After all,

doesn't air resistance act to slow an object down?Wouldn't the object with greater air resistance fall

slower?

Air Resistance

Great Question!

Why is this so?

No worries, Ill find the clue.

Ill open all the books and memorize it.


16/19

Air Resistance


17/19

So in conclusion, the elephant falls faster than the featherbecause it never reaches a terminal velocity; it continues toaccelerate as it falls (accumulating more and more airresistance), approaching a terminal velocity yet never reachingit. On the other hand, the feather quickly reaches a terminalvelocity. Not requiring much air resistance before it ceasesits acceleration, the feather obtains the state of terminalvelocity in an early stage of its fall. The small terminalvelocity of the feather means that the remainder of its fallwill occur with a small terminal velocity.

Air Resistance

I found itGood Boy


18/19

My name is Dana Santika

And youve already learned about the concept of free fall

Thank you very muchGalau


19/19

Falling Object_Dana Santika_Physics Educational Department of Undiksha

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