Transcript Forces in One Direction

In order to change the motion
Of an object, you must apply
A force to it.
A force is the cause of an
Acceleration, or the change
In an object’s motion.
Force is a VECTOR quantity!
The SI unit of force is the Newton,
Labeled with an, N.
The Newton is a derived unit
Named after the famous
Isaac Newton.
It is a derived unit that comes
From multiplying acceleration
By mass.
1 N = 1kg X 1 m/s2
Forces can act through contact
Or at a distance.
Contact forces are forces that
Arise from the physical
Contact of two objects.
Field forces are forces that
Act across a distance, not
Through contact.
(i.e. magnets or gravity)
In order to show forces on paper,
We use force diagrams.
A force diagram is a diagram of
The objects involved in a situation
And the forces exerted on
The objects.
Another way of showing the
Forces involved on an object
Is a free body diagram.
It is basically a force diagram
That has only an isolated object.
An object at rest remains at rest,
And an object in motion continues
In motion with constant velocity
(that is, constant speed in a
Straight line) unless it experiences
A net external force.
The tendency of an object not
To accelerate is called inertia.
The net external force is the
Total force resulting from a
Combination of external forces
On an object; sometimes
Called the resultant force.
Inertia is directly related to
The mass of the object.
The greater the mass, the less
The object will accelerate under
A given force.
Equilibrium is the state of a
Body in which there is no
Change in its motion.
The acceleration of an object is
Directly proportional to the net
External force acting on the
Object and inversely proportional
To the mass of the object.
This is much easier to write
As an equation…
F = ma
FORCE
SYMBOL
Definition
Direction
Friction
Ff
The contact force that acts
to oppose sliding motion
opposite the
direction of sliding
Normal
FN
The contact force exerted
by a surface on an object
Perpendicular to
the surface
Spring
Fsp
The pull or push a spring
exerts on an object
Opposite the object
at end of spring
Tension
Ft
The pull exerted by a
string or rope when
attached to a body
Away from object
and along string
Thrust
Fthrust
A general term for the
forces that move rockets
or planes
Same direction of
acceleration
Weight
Fg
A long-range force due to
gravity between objects
Straight down to
the center of earth
The normal force is a contact
Force exerted by one object on
Another in a direction
Perpendicular to the surface
Of contact.
The normal force is always
Perpendicular to the surface,
Not necessarily opposite the
Force of gravity.
F = ma
The weight of an object is
The magnitude of the force
Of gravity acting on that object.
w = mg
A 5.5 kg watermelon is pushed
Across the table. If the
Acceleration of the watermelon
Is 4.2 m/s2 to the right, find
The net external force.
F = 23 N to the right
A ball is pushed off with a force
Of 13.5 N accelerates at
6.5 m/s2 to the right. What is
The mass of the ball?
2.1 kg
The constant velocity that is
Reached when the drag force
Equals the force of gravity is
Called the Terminal Velocity.
The terminal velocity of a person
Out stretched is about
60 m/s!
An interaction pair is a
Pair of simultaneous equal but
Opposite forces resulting from the
Interaction of two objects.
If two bodies interact, the
Magnitude of the force exerted
On object 1 by object 2 is equal
To the magnitude of the force
Simultaneously exerted on object
2 by object 1, and these two forces
Are opposite in direction.
This is better stated as
For every action, there is an
Equal by opposite reaction.
When a softball with a mass of
0.18 kg is dropped, its acceleration
Is g. What is the force on the
Earth due to the ball, and what is
Earth’s acceleration?
Earth’s mass is 6.0 X 1024 kg
1.8 N
1.8 N
2.9 X 10-25 m/s
A 50 kg bucket is being lifted by a
Rope. The rope will not break if the
Tension is 525 N or less. The bucket
Started at rest, and after being lifted
3 m, it is moving at 3 m/s. If the
Acceleration is constant, is the
Rope in danger of breaking?
570 N, yes it will break!
There are only 4 fundamental
Forces of nature…
Gravitational Forces
Electromagnetic Forces
The Strong Nuclear Force
The Weak Nuclear Force