Download Newton`s Laws Outlines

Newton’s Laws Outline
Force
A ____________________or _____________________ that starts,
stops, or changes the direction of an object.
The unit for measuring force is a ___________________________,
named after Sir Isaac Newton the scientist who explained how
forces and motion relate to each other (better known as Newton’s
Three Laws of Motion, which we will be covering shortly).
They are represented by the size and length of
________________________
Large Force
Medium Force
Small Force
Forces transfer _______________ to an object.
Let’s list some forces on the lines below.
_________________________
_________________________
_________________________
_________________________
_________________________
_________________________
___________________________
___________________________
___________________________
___________________________
___________________________
___________________________
Forces can act in all ______________________ as well as acting
______________________ each other.
Forces act on any object with mass at _______ times.
Drawing Forces (aka Free-Body Diagrams)
 Arrows are used to represent force strength and direction. The
bigger the arrow, the stronger the force.
Fn = _________________________
Fg = _________________________
Fa = _________________________
Ff = _________________________
Fb = _________________________
Flift = __________________________
Now draw force diagrams for the following items in the space below
1. Airplane
Types of forces for diagramming.
2. Boat
Normal (Fn) Lift (Flift)
Air Resistance (drag) (Ff)
3. Bicycle
Applied (Fa) Buoyancy (Fb)
Friction (Ff)
Friction
Gravity (Fg)
_____________________________________________
______________________________________________
Balanced & Unbalanced Forces
__________________ __________ are equal in size but opposite in
direction, resulting in no motion.
__________________ __________ are unequal in size, resulting in
motion.
Place your hands together and push. Is this a balanced force?
How do you know?
Place your hands facing away from your chest and push. Is this a
balanced force? How do you know?
_______ ___________ is the amount of force left over after 2 forces
combine or collide with each other.
Forces in the same direction add.
+
=
EXAMPLE: Pushing a car
Forces in opposite directions subtract.
EXAMPLE: Tug of War
+
=
Calculate the net force in the problems below:
1.
2.
3.
4.
net force = _______
net force = _______
net force = _______
net force = _______
___________________________________________________
_____________________________________________________________
_____________________
______________________________________________
Friction
Any object, no matter how ________________ will have
___________________bumps that are not noticeable to us because they
are so small.
__________________ is a force that opposes motion. It comes from
objects rubbing against one another.
Type of Friction
Definition
Examples
Reducing Friction
Materials that reduce friction are called _____________________.
Friction can _______________ be eliminated.
Examples:
1.
2.
3.
4.
_______________________
_______________________
_______________________
_______________________
If a feather and a coin were dropped from the same height at
exactly the same time, which would hit the ground first? Why?
What about in the absence of air resistance? Why?
What about skydivers … how do they control the speed of their
descent?
Newton’s First Law of Motion
An object at rest will stay at rest, an object in motion will stay in
motion, in a straight line, at a constant speed, until an outside force
acts on it.
THINK/PAIR/SHARE - - What are some of the outside forces that
can change motion, either allowing objects to stay at rest or stop them
from moving? ___________________________________________
What can we do about these outside forces that affect our motion?
For example, how can we get rid of friction?
MORE EXAMPLES OF NEWTON’S 1ST LAW:
 What happens to an uncovered drink when a car abruptly
starts/stops/turns?
 What happens to an unbelted car occupant during a front –
end collision?
 Why can some people pull a tablecloth out from under
dishes without knocking anything over?
________________________is the tendency of an object to resist any
change in motion. It is completely dependent upon
_______________________
The more __________________ the more
___________________.
EXAMPLES:
A bicycle rider is no longer pedaling, but the bike keeps
moving forward, why?
What forces act on the bike to slow it down?
Which would have more inertia …
Bowling ball or golf ball?
Car or airplane?
Gallon of milk or a 12 ounce soda?
Newton’s Second Law of Motion
_____________________________________________________________
_____________________________________________________________
Newton understood that _________________, __________________,
and ________________________ are related. He showed that the
motion of an object changes when an outside force is applied (1 st law).
He also showed that knowing the mass and the acceleration of an
object, you could calculate its force (2nd law).
Today this observation has been restated as the SECOND LAW OF
MOTION, the net force on an object equals its mass times its
acceleration
_____________________= ______________X
__________________
If the force remained constant
and mass increased, acceleration would
 __________________.
 and mass decreased, acceleration would
__________________.
If the mass remained constant …
 and acceleration increased, the force would
____________________.
 and acceleration decreased, the force would
____________________.
EXAMPLE:
Walking versus
running into a
wall !
Example Word Problems
1. How much force is needed to accelerate a 20 kg
crate by 3m/s/s?
1. mass = _______________________
2. acceleration = __________________
3. force = _______________________
How much force must be added to the
2. push it with 120 N of force?
1. mass = _______________________
2. acceleration = __________________
3. force = _______________________
What is the force applied to each cart?
Use your formula!!!!!!
a = 2.5 m/s2
30.0 kg
a = 1.5 m/s2
Force = ________
30.0 kg
Force = ________
20.0 kg
How much force would you need to add to the cart on the right if you
want to accelerate it to 2.5 m/s/s just like the one on the left?
Newton’s Second Law of Motion can also be used to calculate an
object’s weight.
 WHY? Because we know that your weight is calculated by the
acceleration of gravity (9.8 m/s/s) X whatever your mass is.
Each planet has a different acceleration of gravity because gravity is
dependent upon the size of the planet. So how would your weight
differ from planet to planet?
___________________________________________________
___________________________________________________
All objects accelerate at 9.8 m/s/s. However all falling objects are
affected by __________________________, which can cause
different objects to actually fall faster. When one object stops
accelerating because of air resistance, the object has reached its
______________________ _______________________.
What types of objects would probably reach terminal velocity very
quickly as the fall?
___________________________________________________
Falling objects also experience __________________________.
While an object is in freefall, the weight of the object is zero. This is
because there is nothing to ____________ _______________ on
the falling object. This leads us into the third law of motion.
Newton’s Third Law of Motion
When one object exerts a force upon a second object, the second
object exerts and equal and opposite force upon the first object … OR
…
________________________________________________________
________________________________________________________
When you sit on a chair, your body exerts a force on that
______________, the chair in turn exerts a force on
your_______________. This is why you do not fall through the chair.
When you place a book on a table, the book exerts a force on
that____________________, the table in turn exerts a force on the
_______________________.
In the example of the balloon, the force propelling the balloon is equal
and opposite to the force of the air leaving the balloon.
Apply Newton’s Three Laws of Motion
DIRECTIONS: Use your group, your textbooks, your notes, and your
prior knowledge of Newton’s Three Laws of Motion to answer the
following questions IN COMPLETE SENTENCES.
Part A: Newton’s First Law of Motion and Friction
1. Recall or find Newton’s First Law of Motion and write it here.
2. Newton’s first law is sometimes called the “Law of Inertia”. Write
the definition of inertia below. What is inertia solely dependent
upon?
3. If Newton’s first law is true, then, consider the following questions
and try to answer them:
a. Why won’t a book slide forever if I give it a push across the
floor?
b. Why do I need a gas pedal in my car? Can’t I just give my car a
little push and it will roll forever?
c. What force is acting on the book and car to slow them down?
4. Imagine a place in space, far from all gravitational and frictional
forces. Suppose that an astronaut throws a rock. The rock will:
(Circle your answer.)
a. gradually stop.
b. continue in motion in the same direction at constant speed.
5. Ben Too Close is being chased through the woods by a bull moose
which he was attempting to photograph. The enormous mass of the
bull moose is extremely intimidating. Yet, if Ben makes a zigzag
pattern through the woods, he will be able to use the large mass of the
moose to his own advantage. Explain this in terms of inertia and
Newton's first law of motion.
Part B: Newton’s 2nd Law of Motion
1. State Newton’s 2nd Law of Motion and write the formula that
explains Newton’s 2nd Law. Define each variable in the formula.
2. What two factors affect the rate of acceleration of an object according
to Newton’s 2nd Law?
3. According to Newton’s 2nd Law, what happens to the acceleration of
a rocket if the net force is doubled?
4. Find Acceleration.
a. What is the acceleration of a 500kg corvette if the net force on
the corvette is 2,000N?
b. What is the acceleration of a 1,000kg car if the net force on the
car is 3,000N?
c. The net horizontal force on a 50,000kg railroad boxcar is
4,000N. What is the acceleration of the boxcar?
d. A fully equipped astronaut has a mass of 150kg. If the
astronaut has a weight of 555N standing on the surface of
Mars, what is the acceleration due to gravity on Mars?
5. Find the Net Force.
a. What is the net force needed to accelerate a 50.0 kg bowling
ball at 2.0m/s2?
b. A skydiver with a mass of 80.0 kg is accelerating at 4.0 m/s2.
What is the force of the air resistance acting on the skydiver?
c. An unbalanced force gives a 2.00kg mass an acceleration of
5.00m/s2. What is the force applied to the object?
d. A racing car has a mass of 710kg. It starts from rest and travels
120m in 3.0s. The car undergoes uniform acceleration during
the entire 3.0s. What is the unbalanced force applied to the
car?
6. Find the Mass.
a. If a skydiver has a net force of 400N and an acceleration of
5m/s2, what is the mass of the skydiver?
b. A child on roller blades accelerates at 5.0 m/s2, due to a
horizontal net force of 18.0N. What is the mass of the child?
c. An unbalanced force of 20N gives a stone an acceleration of
4.0m/s2. What is the mass of the stone?
d. An unbalanced force of 25N is used to accelerate an object at a
rate of 2.1m/s2. What is the mass of the object?
Part C: Newton’s 3rd Law and Momentum
1. State Newton’s 3rd Law.
2. Explain how Newton’s 3rd Law is at work when you walk.
3. Or when you are just standing on the ground.