force - Physics Bucket

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14 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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FORCES

Forces and motion

FORCE


What is a FORCE?


A

FORCE

is a
push or pull

upon an object
resulting from the object's

interaction

with another
object.


Whenever there is an

interaction

between two objects,
there is a force upon each of the objects.


When the

interaction

ceases
, the two objects no longer
experience the force.


Forces

only exist as a result of an interaction.

Source: http://www.physicsclassroom.com

FORCE


What is the SI unit of force?


The
SI unit of force
is
kg m/s
2

, which is equivalent
to a
newton, N
.




EXAMPLE:

A force of 20 kg m/s
2

is the same as
a force of 20 N.

MECHANICAL FORCE

What is a MECHANICAL FORCE?


Any type of force that results when two interacting
objects are in
direct contact


Also called
CONTACT FORCE


Includes: (1) Normal force, (2) Frictional force, (3)
Tensional force, and (4) Applied force


NORMAL FORCE, N

Support force
exerted
perpendicular
to the surface
of contact

N

FRICTIONAL FORCE, f

Force that
tends to
resist

the
relative
motion
of
surfaces in
contact

f

APPLIED FORCE, F

Force exerted
on objects by
man or other
objects

F

WEIGHT, W

Pull of gravity
on objects

W

ANSWER: Gravitational force is the force of attraction between masses

Compare weight
and gravitational
force

TENSIONAL FORCE, T

Pulling force exerted by a string, cable,
chain or other similar objects on another
object

T

T

Concept check!


Which of the forces are
contact

forces?


applied force,
friction, tension,
normal force


Which of the following forces is a
non
-
contact

force?


gravitational force
or weight


Can you name some other non
-
contact forces?

FREE
-
BODY DIAGRAM

Draw a free
-
body diagram of
the forces acting
on

A) the truck; and
B) the wooden
crate.

FREE
-
BODY DIAGRAM

W

N

FBD of the truck

FREE
-
BODY DIAGRAM

W

N

FBD of the crate

f

T

DRAW


A man pushes a cart at
a constant rate.


DRAW THE FREE
-
BODY DIAGRAM
OF THE CART.

DRAW


A sled slides down
an incline.


DRAW THE
FREE
-
BODY
DIAGRAM OF
THE SLED.

DRAW


A man climbs down a
rope.


DRAW THE FREE
-
BODY DIAGRAM
OF THE MAN.

DRAW


A man pushes against the walls
to keep him from sliding down.


DRAW THE FREE
-
BODY DIAGRAM OF
THE MAN.

NEWTON’S LAWS OF MOTION


First Law of Motion


Law of Inertia


An object
at rest
will remain at rest, and an
object
moving at a constant rate
along a
straight line will continue moving with
constant speed along a straight line
UNLESS
ACTED UPON BY AN UNBALANCED FORCE
.

NEWTON’S LAWS OF MOTION


Second Law of Motion


Law of Acceleration


The

acceleration

of a body is directly
proportional to, and in the same direction as,
the

net force

acting on the body, and
inversely proportional to its

mass
.

TO SUMMARIZE:

CLICK ON THE LINK TO OPEN A YOUTUBE VIDEO ON NEWTON’S LAWS OF MOTION

http://www.youtube.com/watch?v=UVdqxYyFRKY

NEWTON’S LAWS OF MOTION


Third Law of Motion


Law of Action and Reaction


For every
action

there is an equal and
opposite
reaction
.

ANALYSIS


Watch the video by clicking on the link below:

http://www.youtube.com/watch?v=Yf0BN0kq7OU


Explain why the three laws of motion presented in
the video are incorrect.


Write your answers on a short bond paper. Your
output can be hand
-
written or printed, following the
format:



Name

Class Number

Year &

Section

Date Submitted


MISCONCEPTIONS ABOUT NEWTON’S LAWS