Mr. Kuffer
Concepts of Physics
NET
applied
Isaac Newton
1642 - 1727
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Isaac Newton was born prematurely and barely survived on
Christmas day, 1642, the same year that Galileo died. Newton’s
birthplace was his mother’s farmhouse in Woolsthorpe, England. His
father died several months before his birth and he grew up under the
care of his mother and grandmother. As a child he showed no
particular signs of brightness, and at the age of 14½ he was taken out
of school to work on his mother’s farm. As a farmer he was a failure,
preferring to read books he borrowed from a neighboring druggist. An
uncle sensed the scholarly potential in young Isaac and prompted him
to study at the University of Cambridge, where he attended for five
years and graduated without particular distinction.
A plague swept through London and Newton retreated to his
mother’s farm—this time to continue his studies. At the farm and at
the age of 23 he laid the foundations for the work that was to make
him immortal. Seeing an apple fall to the ground led him to consider
the force of gravity extending to the moon and beyond, and he
formulated the universal law of gravitation (which he later proved); he
invented calculus, an indispensable mathematical tool in science; he
extended Galileo’s work and formulated the three fundamental laws of
motion; and he formulated a theory of the nature of light, showing
with prisms that white light is composed of all the colors of the
rainbow. It was his experiments with prisms that first made him
famous.
When the plague subsided Newton returned to Cambridge and
soon established a reputation for himself as a first-rate
mathematician. His mathematics teacher resigned in his favor and
Newton was appointed the Lucasion professor of mathematics. He held
this post for twenty-eight years. In 1672 he was elected to the Royal
Society where he exhibited the world’s first reflector telescope,
which can still be seen preserved at the library of the Royal Society in
London with the inscription: “The first reflecting telescope, invented
by Sir Isaac Newton, and made with his own hands?’
It wasn’t until Newton was 42 that he began to write what is
generally acknowledged as the greatest scientific book ever written,
the Principia Mathematica Philosophiae Naturalis. He wrote the work in
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Latin and completed it in 18 months. It appeared in print in 1687 and
wasn’t printed in English until 1729, two years after his death. When
asked how he was able to make so many discoveries, Newton replied
that his solutions to problems were not by sudden insight but rather
by continually thinking very long and hard about them until he worked
them out.
At the age of 46 his energies turned somewhat from science
when he was elected a Member of Parliament. He attended the
sessions in Parliament for two years and never gave a speech. One day
he rose and the House fell silent to hear the great man. Newton’s
“speech” was very brief; he simply requested that a window be closed
because of a draft.
A further turn from his work in science was his appointment as
warden and then to master of the mint. Newton resigned his
professorship and directed his efforts toward greatly bettering the
workings of the mint, to the dismay of counterfeiters who flourished
at that time. He maintained his membership in the Royal Society and
was elected president and re-elected each year for the rest of his
life. At the age of 62 he wrote Opticks, which summarized his work on
light. Nine years later he wrote a second edition to his Principia.
Although Newton’s hair turned gray at thirty, it remained full,
long and wavy all his life, and unlike others in his time, he did not wear
a wig. He was a modest man, was very sensitive to criticism, and never
married. He remained healthy in body and mind into old age. At eighty
he still had all his teeth; his eyesight and hearing were sharp, and his
mind alert. In his lifetime he was regarded by his countrymen as the
greatest scientist who ever lived. In 1705 he was knighted by Queen
Anne. Newton died at the age of 85 and was buried in Westminster
Abbey along with England’s kings and heroes.
Newton showed that the universe ran according to natural laws
that were neither capricious nor malevolent—a knowledge that
provided hope and inspiration to scientists, writers, artists,
philosophers, and people of all walks of life, and that ushered in the
Age of Reason. The ideas and insights of Isaac Newton truly changed
the world and elevated the human condition.
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Isaac Newton
(1642- 1727)
Prior to Isaac Newton’s Birth
1625 - Last major outbreak of Bubonic Plague.
1642 (October) - Isaac Newton Sr. (young Isaac’s father) passes away.
Isaac Newton is Born
1642 (Dec. 25) - Galileo dies. Later that same year Isaac Newton is born. He
almost died during the birth.
- Born into the Yeoman (working) class in Woolsthorpe
Lincoinshire, England.
Boyhood
- Isaac was brought up by his grandmother and mother,
(who eventually remarried).
- Isaac attended Grantham Free Grammar School. He stayed with a host
family (the Clarks) for his schooling there.
1656 - Isaac returns to Woolsthorpe to work on the farm at his mothers request.
Age 14 ½ .
1659 - Isaac starts to compile a notebook of his thoughts and studies of Euclid,
Galileo, and others.
1660 - Newton finalizes his Grantham education.
Higher Education
1661 (June 5) - Begins Schooling at Trinity College in Cambridge.
- Continues to compile notebooks of his studies.
1662 - Develops a deep religious fervor. List all of his sins in a coded shorthand.
1665 - Introduces integration and Calculus to mathematically explain the world
around him.
1665 (June / July) - Isaac returns home due to the Plague. (June 7, Plague
infection in London).
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1666 (January) - Isaac develops his Theory of Colors. He uses a prism to show all
colors present in light.
1666 (March 20) - Isaac returns home due to Plague.
1667 (April) - Returns home after earning a Bachelor of Arts degree.
1668 - Isaac Newton earns his Masters of Arts degree.
** 1667- 1668 - Isaac revolutionized work in Optics
- Studied space and time, chemical experiments, and mathematics.
** 1669- 1673 - Newton became a Professor of Mathematics and Chemistry at
Cambridge.
Emergence into Public Life
1687
- The Principia is published
- A publication of his works done at Cambridge (Optics, Mathematics,
Chemistry, and Mechanics).
1693 - Mental Breakdown
1699 - Became Master of the Mint
1705 - Newton was knighted by Queen Anne of England.
1713 - Publication of the Second Edition of The Principia.
1726 - Publication of the Third Edition of The Principia.
1727 - Isaac Newton died at the age of 85, and was buried at
Westminster Abbey with the kings and queens of England.
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Forces
I.
Contact vs. Long-Range:
A) contact forces – push or pull on an object through
touching it (contact)
B)
Long range – push or pull on an object without direct
contact
C)
Agents – cause of force (i.e. “applied”, gravity,
“normal”, friction, … among others)
II.
Newton’s 1st Law:
A) An object at rest will remain at rest and an object in
motion will remain in motion (with a constant velocity),
unless acted on by an outside force.
B)
Inertia – Tendency of an object to resist change in
motion
C)
Equilibrium – an object is in equilibrium if it is at rest
or moving with a constant velocity (note: rest is a
constant velocity of zero). (For this to be achieved the
NET force has to be zero, more about this later)
III. Newton’s 2nd Law:
A) Experiments show that the acceleration of an object
is proportional to the net force and inversely
proportional to its mass (a = F/m)
B)
More commonly written as F = ma
IV. The Newton:
A) A Newton is the amount of force it takes 1 kg to
be accelerated at 1 m/s2. Therefore the unit Newton
(N) is equal to 1 kg·m/s2.
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V.
Newton’s 3rd Law:
A) Whenever one object exerts a force on a second
object, the second object exerts an equal and opposite
force on the first object.
B)
This is referred to as ‘Action – Reaction’ pairs.
VI.
Free Body Diagrams:
(How to represent several forces all at once)
A) Draw the object as a dot (for simplicity)
B)
Show all forces acting on the object (draw vector
arrows in the direction of the force, with their tails on
the dot).
FN
Ff
FA
Fg
VII. The Normal Force:
A) Often referred to as the ‘support’ force
B)
Example: Gravity pulls down on a book… the desk
pushes back up… Otherwise the book would fall to the
ground… And it doesn’t… why, you ask? Because it is
‘normal’ for the book to not fall… Hence the ‘Normal
Force’
VIII.The NET Force:
A) The Net Force (notice the different subscript… ‘NET’)
is a combination of all forces acting on an object.
B)
If we say it has no NET force, we mean that all of the
forces add to zero… not that there is no force on the
object.
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IX.
Mass vs. Weight:
A)
B)
C)
D)
X.
Differentiate between mass and weight…
Apparent weight – force exerted by a scale
Weightlessness – an apparent weight of zero
W = Fg = mg
Example Problems:
Mass vs. Weight
Your mass is 75 kg. You stand on a scale in an elevator that
is going up at 2.0 m/s2. What is your apparent weight? Is this
larger, smaller, or equal to your weight at rest?
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Newton’s 1st Law
Name:_________________
Date:__________
Circle the correct answer. Write a clear and concise explanation .
Luke Autbeloe drops a 5.0 kg box of shingles (weight approximately 50.0 N) off the
barn house roof into a haystack below. Upon hitting the haystack, the box of shingles
encounters an upward restraining force of 50.0 N . Use this description to answer the
following questions.
1. Which one of the following velocity-time graphs best describes the motion of
the shingles? Support your answer with sound reasoning.
2. Which one of the following ticker tapes best describes the motion of the falling
shingles from the time they are dropped to the time they hit the ground? The arrows
on the diagram represent the point at which the shingles hit the haystack. Support
your answer with sound reasoning.
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3. Several of Luke's friends were watching the motion of the falling shingles. Being
"physics types", they began discussing the motion and made the following comments.
Indicate whether each of the comments is correct or incorrect. Support your
answers. (true or false)
_________
Once the shingles hit the haystack, the forces are balanced and the
shingles will stop.
_________
Upon hitting the haystack, the shingles will accelerate upwards
because the haystack applies an upward force.
_________
Upon hitting the haystack, the shingles will bounce upwards due to
the upward force.
4. If the forces acting upon an object are balanced, then the object
A. must not be moving.
B. must be moving with a constant velocity.
C. must not be accelerating.
D. none of the above.
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Inertial Balance Lab
Relevant Theory:
Generally, a scale determines an object’s weight and/or mass by using springs and
understood value for the acceleration due to gravity. The use of these scales is
dependent on the presence of gravity.
In an anti-gravity environment, these scales would be useless. Aboard the space
shuttle, the mass of an astronaut is determined by the use of an inertial balance.
An inertial balance determines the mass of an object by detecting how quickly the
object can vibrate back and forth. More massive objects vibrate slowly, and less
massive objects vibrate more quickly. In this lab, we will use an inertial balance to
determine the mass of an unknown mass in this different way.
Procedure:
Using the large C-clamp, clamp the inertial balance to the table so that it can
vibrate freely over the tables’ edge. Using the small C-clamp provided in class,
clamp 10.0 g of mass in the swinging tray of the inertial balance.
Using a stopwatch, determine as precisely as possible how long it
takes for the inertial balance to make 20 complete oscillations
(over and back movements). Write this time in the data table.
Repeat the above procedure with the following masses (20, 30, 40,
50, 75, 100, 200, 300, 500 grams). The last row leave blank for
your own mass.
mass
10
20
30
40
50
75
100
200
300
500
Data Table
t for 20 osc
Analysis and Conclusion:
1. Create a data table including columns for; mass, time for 20 oscillations,
time per one oscillation, time for one oscillation2.
2. On Excel, plot a time [(one oscillation)] (y axis) vs. mass (x axis) graph.
3. Describe the graph of time versus mass. What does the graph mean?
4. Interpolate to find the mass of the unknown mass. Show your interpolation
lines on the graph.
5. Determine the percent error of your unknown mass. To do so, you first have
to measure the actual mass of the unknown using the scale provided.
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t for 1 osc
t2