Transcript Force – Concept Overview

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Force – a push or pull (in a certain direction)
Forces are present in all mechanical systems
Amount of push/pull (magnitude) is
represented in units:
a) Newtons (N) in the SI/metric system or;
b) Pounds (Lbs) in the English system
Force is a vector quantity because it has a
magnitude and direction  5N (fwd)
A quantity that has a magnitude only (and no
direction) is called a scalar  Mass puck=0.05kg
Makes sense right? Can’t have mass or temperature in a direction????
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The symbol for all vector quantities is a letter
with a half arrow on top (ex. F).
Ex: Malyka kicks the ball with a force of
5N[East]  notice magnitude with unit and direction in parentheses
Therefore,
F ball=5N[East]
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the interaction of forces can be described by Newton’s 3
Laws of Motion
Newton’s 3 Laws of Motion:
1.
Object in motion stays in motion or at rest stays at rest
until external force acts on it (also known as inertia)
 When no outside forces act on an object, or all
forces acting on it are equal, that object is in
equilibrium(balance)
2.
Acceleration of an object is proportional to the force
applied to that object (F=ma). The greater the force the
greater the acceleration and visa versa.
3.
For every force applied there is an equal and opposite
reaction force applied back.
System Diagram
FBD
FN
a)
FG
FAIR
b)
FG
c)
FF
FN
FG
FA
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A Free Body Diagram(FBD) is used to represent the
interaction of all forces in a system
It is important to understand the different types of
forces:
Symbol
Description
Applied
Normal
Friction
Gravity
Air Resistance
Tension
Spring
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A Free Body Diagram(FBD) is used to represent the interaction of all
forces in a system
It is important to understand the types of forces that might be present:
Type of Force
Symbol
Description
Applied
Fapp (Fa)
An applied force is a force which is applied to an object by a person or another object.
Normal
Fnorm (Fn)
The normal force is the support force exerted upon an object which is in contact with
another stable object.
Friction
Ffrict (Ff)
The friction force is the force exerted by a surface as an object moves across it or makes
an effort to move across it.
Gravity
Fgrav (Fg)
The force of gravity is the force with which the earth, moon, or other massively large
object attracts another object towards itself.
Air Resistance
Fair
The air resistance is a special type of frictional force which acts upon objects as they
travel through the air.
Tension
Ftens (Ft)
The tension force is the force which is transmitted through a string, rope, cable or wire
when it is pulled tight by forces acting from opposite ends.
Spring
Fspring (Fs)
The spring force is the force exerted by a compressed or stretched spring upon any
object which is attached to it.