Laws of Motion Interview

5/12/2018 Laws of Motion Interview - slidepdf.com

http://slidepdf.com/reader/full/laws-of-motion-interview 1/12

LAWS OF MOTION interview

Objectives:• to role play three famous scientists

• to discuss the contribution of each scientist to the Laws of Motion

•

to be aware of the changes in ideas about motion through the centuries• to learn Newton's 3 Laws of Motion

Materials - Class Set :• Brief Biographies of Aristotle, Galileo, and Newton

• Aristotle Interview

• Galileo Interview

• Newton Interview

• Funny Wizard Hat

• Self Quiz- Can be taken online or photocopied

Procedure:

1. Hand out Interview Sheets

2. Have students sit in a circle and chose 2 volunteers for each interview.

3. The Interviewer is a Wizard and wears a funny hat

4. Briefly introduce each scientist to the class

5. Have students act out interview.

6. Discuss the main points that are addressed in the Summary

7. Open floor for questions

8. Proceed to next Interview

Analysis/Results/Conclusion:

Have students complete self quiz and write a brief summary of what they learned

____________________________________________________________________

Script

ARISTOTLE

All right, wasn't that time travel amazing! Well, we are going to try and find

Aristotle.Before we talk to him, let me warn you! We came here to visit him, not because he was right, but because he was wrong! His ideas were believed to be true

from 500 BC to 1600 CE. That's about 2000 years of false knowledge. What Aristotle

taught, appeared to be correct because it seemed obvious, but not all things are

obvious.

" Wait, I see him now." There he is! Lets go talk to him. "Hello Aristotle!"

http://library.thinkquest.org/11924/aristotleinfo.html

http://library.thinkquest.org/11924/galileoinfo.html

http://library.thinkquest.org/11924/newtoninfo.html

http://library.thinkquest.org/11924/aristotle.html

http://library.thinkquest.org/11924/galileo.html

http://library.thinkquest.org/11924/newton.html

http://library.thinkquest.org/11924/gather/mcq1.html


http://library.thinkquest.org/11924/galileoinfo.html








"Great Zeus! You seem to be a god that has descended from the heavens. That hat of

yours is enigmatic of your strength. I am at your mercy, oh Great One"

"Thanks, for the praise, but I'm no god, but for your purposes, I am a person who

wishes to know more about your theory about the motion of objects"

"Ahh yes, I'd love to share that with you. I believe all motion is linear on the planet

Earth: meaning everything moves in a straight line. Let me show you. If I throw this

rock, it will travel in a straight line, and also fall in a straight line….

The way Aristotle thought

projectiles moved

The way projectiles

"really" move

In addition, when I drop this feather and rock at the same time, the rock will fall to the

ground first. Why you ask? Well, that's because I believe that the Earth pulls on

objects according to their weight.This means that a large heavy object will fall to the

ground faster than a large light object."

The way Aristotle 'saw'

objects to fall on the Earth

As we know, or will

know in the next few sections, objects

actually fall like



this in a friction free environment (vacuum)

"Is that all Aristotle?"

"Of course not, there also exists a natural motion with each object. This is the motion

an object has when it is as rest and when it is moving in a straight line at uniform

speeds. This natural motion is also prevalent in the heavens - the great glass spheres

that rotate around the center of the universe - our planet Earth."

"Ummm yes?!? Well Aristotle, how do you account for motion that isn't at constant

speeds??"

"Well my under-educated friend, this is what I call violent motion. You see motion

also depends on an applied movement. Once this movement stops, the motion of theobject stops. For example, if I push this cart, the cart keeps moving until I stop

pushing. That's all I'm going to talk about today. Good day sir."

Well, I hope you see how Aristotle's view on motion seems to make sense.Unfortunately, it isn't correct. But because his theories appeared to make sense, they

became popular and well accepted for a very long time. The key ideas that Aristotle

tried to teach were:

All motion on the Earth is linear .

All motion in the heavens (outer space) is curved .

The speed at which an object falls is directly related to the mass of an object .

Motion could be considered in two main factions: natural and violent.

Motion continues so long as there is only an applied motion to an object. Removing

the motion stops the object.

http://library.thinkquest.org/11924/media/mot1.ram



It would take a man named Galileo to start the wheels of change in this field of

knowledge called physics.

Click on the time machine to proceed to visit the next person on our voyage: Galileo

__________________________________________________________

GALILEO

Here we are, in jolly old Italy. The time is about 1600, and as I promised we are going

to meet the man with the name that makes us all laugh. "Galileo Galilee" Ah ha , there

he is. "Hello Mr. Galilee. Could I ask you a few questions, please?" .

"Sure sir, only just don't poke my eye with your *enchanted* hat."

"Okay. I wanted to know, what do you think about motion?"

"Well I have a lot to say but I'll try to make it quick. First, I think, unlike Aristotle,

that motion to the Earth does not depend on the weight of an object. Rather, I believe

all objects fall to the ground at the same speed. Let me show you an experiment I did

on top of the leaning Tower of Pisa."







This is what Galileo would have seen at Pisa - two balls with unequal masses both fall in the

same time. (There was little wind on the day of Galileo's experiment, so friction was minimal)

"So you see, the speed at which an object falls at has nothing to do with the mass of

the object. All objects that are released from the same starting point reach the groundin the same time. My theory unlike Aristotle unifies the concept of what I call force

and mass."

"WOW! That's an amazing observation Galileo, but if you're right why then does a

feather not fall in the same time as say a rock??"

"Well my friend, you see I have asked myself the same question, and I came up with

an answer that I think you would find particularly interesting. I think that all objects

have an opposing force to motion - a force that retards the motion. This is the force

that slows down the feather - the flat and thin surface of the feather is pushed up bythe retarding forces in the air. The rock, because it is more sleek, is less prone to these

effects, and hence falls to the ground in less time. My theory though is that if the

feather and the rock were placed in a vacuum (absence of all matter) they would fall

in the same time - it is the air that slows down the feather not the Earth."

"Very true Galileo, now I have also heard that you have had some theories about

motion in general - why objects don't stop immediately as soon as you remove an

applied force - as Aristotle thought."

"Quite true, you see I played a mind game with myself a while ago - I saw that whenyou roll a ball down a ramp such that it rises up the path in its path, that the ball

essentially rolls up the plane to its original height. But in time, the ball slows down,

not reaching the original height it had to begin with I wondered, and asked myself

what slows down the ball - well, like the feather, I figured there must be some form of

resistance on the ball slowing it down, only it was not the air this time, but the surface

of the ball and the plane. I called this force friction. It explains why when you push a



cart the cart slows down to a stop when you stop pushing - the friction opposes the

motion of the cart, hence slowing it down. Back to the plane, if the angle of the

second ramp were to decrease, the ball would 'try' reach a height original to the

release height. Now this model assumes there is no opposing force - friction. I thought

about this model some more and realized that if the angle of the second ramp was

made to approach 0, the ball would keep rolling in a straight line in constant speed.

The above depicts the thought experiment Galileo "thought of" (Now doesn't that make sence!)

This 'observation' gave me a revelation and prompted me to hypothesize that all

objects want to move in a straight line at constant speeds. What prevents them from

doing so is an external unbalanced force, like friction. This deduction prompted me to

think of another observation of objects - since they all want to stay in motion in astraight line in constant speed, they resist changes in motion by trying to stay in

motion - a property I call Inertia. If that sounds complicated, let me give you an

example. When you're pushing a cart loaded with packages, while you are moving

with a constant speed, the package remains at rest on the cart. However, if you

suddenly brake or stop the cart, the package on the cart slide to the front of the cart.

Why? Because the package had inertia to stay moving at the original speed of the cart.

It wanted to maintain that balance. Now you may ask what stops the package from

continuing its intent, well, as I mentioned, friction slows the package as it moves, and

if the package hits anything on its way, its motion is retarded by it as well."

Note how the package slows down, and does not move at a constant (uniform) speed. The package is affected by the retarding force of friction

"Very good points Mr. Galilee, thank you for your time, and I hope things go well for

you."

"Well thank you Mr. Wizard type of person sir, I hope you get a better hat. Goodday!"

Well to give you a summary of our conversation with Galileo, he essentially stated

that all objects when released from the same point, reach the ground in the same time,

providing a minimization of air resistance. In fact, the hypothesis Galileo had was

right, as when the same experiment with the rock and the feather was performed in a



vacuum, some decades later, both fell to the ground in the same time, as there was no

air resistance on the feather or the rock. In case you don't know a vacuum is when

there is no matter in a volume. In case this concept isn't very clear, don't worry, as our

conversation with Newton will help to clear this up. In addition to this, Galileo spoke

of his famous thought experiment, that led to the conclusion that all objects want to

move in a straight line at a constant speed. This property of an object wanting to

maintain this property was called inertia. The final point Galileo spoke of in our

conversation was that all objects have an opposing force called friction that slows the

object down.

We will talk to Galileo again, but for our next lesson in Motion, we will hear from the

man who was thought as the father of physics - Sir Isaac Newton. So to voyage to his

neck of the woods, click on the time machine.

According to Galileo, the motion of a falling object is independent of mass.

Meaning two objects of unequal masses will fall to the ground when dropped from a

set height in equal times

The reason why objects did not always fall in the samwe time was because of a

retarding force called friction.







NEWTON

Our voyage in time now takes us to the land where tea, cricket and the Spice Girls are

popular. That's correct, we're in England. Here we will meet perhaps the most

revolutionary scientist in history, Sir Isaac Newton. In fact, here he is right now!

"Hello Mr. Newton sir, can I ask you a few questions please??"

"Ahh! What hideous kind of hat is that??"

"Um yah, I've been getting comments about it. Now, about those questions, would you

please explain to me and my Internet friend here, your laws of motion you discussed

in your book Principia?"

"Of course. Well my first law really isn't my law at all. I borrowed it from Galileo and

got the credit, but it's okay since Galileo 'borrowed' ideas as well. Anyway, my first

law is that An object will maintain its state of rest or constant speed in a straight lineunless acted upon by an external unbalanced force. In other words, bodies want to

stay in motion in a straight line at a constant speed, or at rest. This was referred to by

Galileo as inertia. Thus, objects try to resist changes in motion when acted upon by anexternal unbalanced force. Thus, my first law attempts to set up or describe motion's

tendencies. My second law relates this property to mathematics and explains why

objects move. My second law states: When an external unbalanced force is applied to

an object at rest or in constant speed in a straight line, the object accelerates in the

direction of the unbalanced force. Furthermore, the acceleration of the object isdirectly proportional to the net forces acting on the object, and inversely proportional

to the mass of the object being accelerated "

"Wow that's a mouthful Newton, perhaps you could simplify that a bit for me."

"No problem. Essentially when you apply forces (a push or a pull), the sum of all the

forces is the direction in which the object accelerates. If the object is really heavy, it

won't accelerate as fast; whereas if it's light, and the same force is applied, the object

will have a greater acceleration. Mathematically this relationship is as follows:

F=ma



(F is the sum of all the forces acting upon the object, m is the mass of the object, and a

is the acceleration of the object.)

So you see, this relationship allows us to predict which way and with what

acceleration an object will move when a certain specified net force is applied to an

object."

"That is totally gnarly dude! Such a simple concept, yet it can be applied for many

practical applications! Tell me more"

"Of course, but only if you refrain from using such awkward tenses of English like

gnarly or dude. Anyway, my third law is perhaps the most recognized, but the most

misunderstood. This law states that: When an object exerts a force on a second object,

the second object will exert a force of equal magnitude, and opposite direction on the first object " This law is most commonly stated as 'for every action there exists an

equal and opposite reaction.' The flaw in this version is that it doesn't say that theforces exerted are on different bodies. Thus, the forces do not simply cancel out as

some may expect, rather they are transferred to the other object. My favorite example

of this law is exhibited by cannon fire. When you fire the cannon, the cannon ball is

pushed forward by an explosion in the cannon.

My law kicks in when the explosion happens. As the bullet is pushed forward by the

gun, the bullet pushes back on the gun. This is seen by the jerk in the rifle when it is

fired. So, the force the gun pushes on the bullet is equal to the force the bullet pushes

back on the gun."

"Fascinating Newton! But I don't understand why when the gun is fired, the gun and

man shooting don't get pushed back as fast as the bullet?"

"Good question. You see if you look back to my second law, force is inversely related

to mass. Because the mass of the bullet is very small compared to the mass of the gun

and man, they don't accelerate backwards as quickly. However, they do get the same

force returned to them. The reason why this force doesn't kill the man is because most

of the 'pain' is absorbed by the barrel of the rifle (gun)."

"Very neat, but I have one more question. Why is it that the man firing the gun doesn'tslide backwards when he fires the gun?"

"An excellent question. You see when the man is pushed back by the bullet, he has a

retarding force exerted upon him. Galileo first noted this force, which I call friction.

This frictional force slows the shooter down very quickly, if he is exerting a lot of

pressure on the ground, or if the ground is very rough. But you see, if the shooter were



to fire his bullet standing on a friction-less surface, then he would be pushed back

such that he would keep moving for ever."

"A very interesting discussion. Thank you for your time Newton."

"A pleasure, and perhaps next time we meet you could change your hat."

"Ha Ha"

There are three main laws of motion Newton described. Firstly:

1.) An object will maintain its state of rest or constant speed in a straight line

unless acted upon by an external unbalanced force

2.) When an external unbalanced force is applied to an object at rest or in constant speed in a straight line, the object accelerates in the direction of the unbalanced

force. Furthermore, the acceleration of the object is directly proportional to the net forces acting on the object, and inversely proportional to the mass of the object being

accelerated (F=ma) "

3.) When an object exerts a force on a second object, the second object will exert a force of equal magnitude, and opposite direction on the first object

In addition to Newton's laws, he discussed the concept of friction. This is the same

force described by Galileo as the retarding force. Although it was not exactly stated

by Newton, the force of friction is related to the amount of pressure you apply at a

point. Friction is not related to area. In general terms, friction is when two dissimilar

surfaces interact with each other creating an opposing force. But, friction also occurs

with objects that are very similar such as glass. If you put two sheets of glass on top of

each other and try to move one of them, you will see that it is very difficult. This is asa result of molecular bonding that forms quickly when the two pieces of glass are put

on top of each other. Thus the two pieces essentially bond to be become one piece.

Since it is hard to break molecular bonds, the person who pushes the glass experiences

difficulty - a resistance force - friction. Thus, friction is also noted to exist when you

exert a force on an object that rests on a similar object.




______________________________________________________________

BRIEF BIO OF THE THREE SCIENTISTS

Did you Know? – GALILEO GALILEIDid you Know? -

Galileo Galilee was born in 1564 and died in 1642. He is most famous for his

many thought experiments in motion. As well, he made astronomical discoveries,

such as the moons of Jupiter.But, Galileo was perhaps best known for his battle with

the Church. He agreed with the philosophy that the planets revolved around the sun.

This heliocentric model was first popularized by Nicholas Copernicus of Poland.

Galileo was a very popular man in Italy and had contacts in high places. Despite this,

he wrote the various publications of his ideas and concepts in Italian as opposed to

Latin. As a result, all the common folk could understand what Galileo was saying.Inspite of Galileo's great contributions to science, the church tried to stop his work. In

fact, they forced him to retract his theories and state that the Earth was the center of

the universe. Galileo's publications were not recognized by the church as late as 1979

- more that 300 years after his death.

If you want more information on Galileo or other scientists, visit one of the following

web pages: A page describing the differences between Aristotle and Galileo

: http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html

A list of many scientist's

biographies: http://hermes.astro.washington.edu/scied/physics/physbio.html

NEWTON

Did You Know? -

Newton Isaac Newton was born in the year of 1642, and died in 1727. He was most

famous for his three laws of motion, but was also known for other major discoveries

in math and science. He compiled most of his work into a masterpiece of sciencecalled the Principia. Newton was known to be arrogant, so his book was written

almost exclusively for the elite and rich. Some people claim that only 50 people in

history have been able to understand his style of writing. Despite his arrogance, he

truly was a father in the field of science. At the age of 18, he had devised a new

system of mathematics called Calculus, and developed three laws which resulted in a

new way of understanding motion.. All of this happened at his farm while the Black

http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html

http://hermes.astro.washington.edu/scied/physics/physbio.html

http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html




Plague swept across England. In the Principia, Newton claimed to have "discovered"

gravity when an apple fell on his head. But, many now believe that this was just a

story told by Newton, and that in real life, he discovered gravity through thinking -

not seeing.

If you want more information on Newton or other scientists, visit one of the followingweb pages: A very comprehensive and detailed account of Newton and his works:

http://csep10.phys.utk.edu/astr161/lect/history/newton.html





http://www.middleschoolscience.com/motioninterview.htm



























Documents

Laws of Motion Interview