Download C10, S3 – Newton`s First and Second Laws of Motion

C10, S1 – The Nature of Force
What is a force?

A ___________ or a _____________.

Like velocity and acceleration, a _______________ is described by its
_______________ and by the ________________ in which it acts.

The strength of a force is measured in the SI unit called the
_________________ (__).

This unit is named after the scientist and mathematician Sir Isaac Newton.

Direction and strength of a force can be represented by an arrow (___________).

Determines whether an object ____________ and in what _____________.
Combining Forces

Typically, more than one single force acts on an object at one time.

________________– The _________________ of all forces acting on an object.

DRAW THE THREE COMBINING FORCES EXAMPLES ON THE BOARD IN THE
SPACE BELOW.
Unbalanced Forces

Whenever there is a ______ force acting on an object, the forces are
_________________.

Unbalanced forces can cause an object to __________________________,
______________________, or ______________________________.

Example : Tug-of-War
Balanced Forces

____________________ Forces – equal forces acting on one object in
______________________ directions.

Each force is balanced by the other.

Balanced forces acting on an object do ________ change an object’s
___________________.

Net force is equal to _______________.
Example Problem:
Two people are moving a refrigerator. One person pushes with a force of 200 N
and the other pulls with a force of 50 N. The force of friction between the ground and
the refrigerator is 150 N. What is the net force acting on the refrigerator?
Draw a model of this example and then solve for the net force.
C10, S2 – Friction and Gravity
Friction

________________ – The _____________ that two surfaces exert on each
other when they _________ against each other.

The strength of the force of friction depends on 2 factors:

1. _____________________________________________________

2. _____________________________________________________
**Friction acts in a direction _________________ to the direction of the object’s
______________________ motion.**
Types of Friction

____________ Friction – friction that acts on objects that are not moving.
* In order to move an object, you must first overcome
___________________ friction.
_____________ Friction – Occurs when two objects slide over each other.
* Due to the _________________ __________________ between two
surfaces.
* Can be useful.
__________________
__________________

____________________ – Occurs when an object rolls across another surface.

Is easier to overcome than _______________ friction.

Engineers need to reduce the friction between the wheels and the rest of
the object.

Example: Pie plates with marbles- sliding/rolling

_______________ friction – Occurs when a solid object moves through a
___________________ or _____________________.

Easy to overcome unlike sliding friction.
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_______________
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_______________
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_______________
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_______________
Gravity

_____________ – A __________ that pulls objects toward each other.

Sir Isaac Newton

__________________________ – states that gravity acts between all objects in
the universe.


Factors that affect the force of gravity:

____________________

____________________
_____________ – measure of the amount of _____________ in an object. The
SI unit of mass is the ________________ (___).

The _________ mass an object has, the ____________ gravitational force it has.

Sun and the planets

______________________

Gravitational force depends on the ____________ between two objects.

The farther two objects are apart, the ____________ their gravitational
force.

Orbital period of the planets around the Sun.

Mercury (88 days), Venus (225 days), Earth (1 year), Mars (1.8
years), Jupiter (11.8 years), Saturn (29.4 years), Uranus (84
years), and Neptune (165 years)
Weight and Mass

Mass is the amount of matter in an object.

_______________ is the amount of gravitational force acting on an object.

Weight varies with the ________________ of the gravitational force but
________________does not.
How are gravity and motion related?

On Earth there are many forces that can act on objects, but what about space?

In the absence of __________ (space/vacuum), objects are only affected by
_____________________.

___________________ – when the only force acting on an object is gravity.

In free fall, the force of gravity is an ________________ force which causes an
object to _____________________

_________________ (32 ft/s²) - this is the ___________________ of an
object due to gravity near Earth’s surface.

Example: For every second an object is falling, its velocity increases by 9.8 m/s.

Object is dropped from the top of a building

Starting velocity 0m/s

After 1 second velocity is 9.8 m/s

After 2 seconds velocity is 19.6 m/s (9.8 + 9.8)

After 3 seconds velocity is 29.4 m/s (9.8+9.8+9.8)

And so on as it falls

REGARDLESS OF MASS ALL OBJECTS IN
FREE FALL
ACCELERATE THIS WAY!
Air Resistance

_______________________ – type of fluid friction that objects falling through
air experience.

An _________________ force exerted on falling objects.

Not the ____________ for all objects (__________________________).


Balled up piece of paper versus a full sheet
Air resistance _________________ with __________________ up to a point.

Eventually the upward force will equal the downward force.

_________________________ – the greatest velocity a falling object will
reach.

Weight of object _________________ the air resistance.
Projectile Motion

How does gravity effect objects that are moving horizontally?

Figure 12

Objects that move _________________ fall at the same _________ as an
object _____________________ straight down.

If two objects are released at the same height at the same time they will hit
the ground at the same time.

How do you correct for this gravitational effect?
C10, S3 – Newton’s First and Second Laws of Motion
First Law of Motion

______________________________________________________________
______________________________________________________________
______________________________________________________________

On Earth ________________ and ________________ are often the
______________________ forces that cause a change in an object’s motion.
Inertia

The tendency of an _____________________________________________.

The first law of motion is also called the ____________________________.

The amount of inertia an object has depends on the ______________ of the
object.
Second Law of Motion

_____________________depends on the object’s ________________ and the
_____________________ acting on the object.

Acceleration = Net force / Mass

___________________, meters per second per second (m/s²)

_________________, newtons (N)

________________, kilograms (kg)
C10, S4 Newton’s Third Law of Motion
3rd Law of Motion

The third law states – If one object exerts a force on another object, then the
second object exerts a force of equal strength in the opposite direction on the
first object.

“____________________________________________________________.”
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Action-Reaction Pairs
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Walking
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Jumping
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Birds flying
Detecting Motion
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Not always possible to detect

Inertia and size of the object

Action-Reaction Forces _________________ cancel.

These forces do not cancel because they are
___________________________________________________.
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FIGURE 16
Momentum

Momentum is a characteristic of a moving object that is related to the mass and
the velocity of the object.

Momentum = mass X velocity

Units – kg•m/s
The more momentum a moving object has, the harder it is to stop.
Law of Conservation of Momentum

Law of Conservation of Momentum – states that, in the absence of outside forces,
the total momentum of objects that interact does not change.

**The total momentum of any group of objects remains the same, or is conserved
unless outside forces act on the objects.**

Momentum may be transferred from object to another, but none is lost.
C10, S5 Rockets and Satellites

Circular Motion –

Objects moving in a circle are always ____________________.

If an object is ____________________ a ____________ must be acting
on it.

_______________________ – any force that causes an object to move in
a ________________ path.

Gravity and Satellites