mechanics (forces, moments and couples - part i)
TRANSCRIPT
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MODULE 02 - PHYSICS
CAT B 1.1
CRAFT MAINTENANCE LICENSE COU
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MECHANICS (FORCES,
MOMENTSAND COUPLES - PART I)
LESSON05
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Mechanic
• What is ‘Mechanics’?• Branch of applied mathematics dealing with motion and forces
producing motion
• Machinery as a subject; engineering
• Way in which something is done or operated
Cont…
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SCALAR AND !ECTOR "UANTITIES
• uantities are thought of as being eitherscalar or !ector
• "erm scalar means that the #uantitypossesses magnitude
• $calar• %ength
• &rea
• 'olume
• $peed
• Mass
• (ensity
Cont…
S # %
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Sca#a$ an% !ec&'$
"(an&i&ie• 'ector #uantities possess both magnitude&)( direction
• *orce is a !ector #uantity
…Cont
Cont…
S # % !
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…Cont Sca#a$ an% !ec&'$
"(an&i&ie
Cont…
S # % !
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…Cont Sca#a$ an% !ec&'$
"(an&i&ie
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TRIAN)LE OF FORCES
• "wo or more forces can be added orsubtracted to produce a Re(#&an& F'$ce
• *orce is a !ector #uantity + can berepresented by an arrow, drawn to a scale
representing magnitude and direction-• "riangle of *orce
Cont…
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TRIAN)LE OF FORCES…Cont
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POLY)ON OF FORCES
Cont…
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POLY)RON OF FORCES…Cont
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COPLANAR FORCES
Cont…
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RE!ISION
• We ha!e learnt• What is ‘Mechanics’?
• What are $calar #uantities?
• What are 'ector #uantities?
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"UESTIONS
• "wo couples with magnitude * act against
each other- "he resultant will be?
• What is a !ector #uantity?
• & #uantity which has si.e but no direction iscalled a?
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MECHANICS (FORCES, MOMENTSAND COUPLES - PART II)
LESSON0*
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If a Force is applied to a body, it will cause that body to
move or rotate. A body that is already moving will change
its speed or direction.
F = ma
F is the force, m = mass of body and a = acceleration.
EFFECT OF AN APPLIED FORCE
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EQUILIBRIUMS
If at any stage a system of forces is applied to a
body, such that their resultant is zero, then that body
will not accelerate or change direction. The systemof forces and the body are said to be in the
euilibrium.
Note: This does not mean that there are no forcesacting! it is "ust that their total resultant or effect is
zero.
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RESOLUTION OF FORCESTwo forces can be !!e! to give a single force #nown
as the $esultant, it is obvious that this single force can be
considered as the addition of the two original forces.
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The single force can be separated or $esolved into
two components, that are m"t"##y $e%$en!&'"#% .
.
RESOLUTION OF FORCES CONT
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%y drawing the right&angled triangle, with the single
force F, and by choosing angle θ relative to a datum,
the two components become F 'in θ and F (os θ.
RESOLUTION OF FORCES CONT
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RAPHICAL SOLUTIONS
• The uantities must be vector uantities.• They must all be the same, i.e. all forces, or all velocities,
etc. )they cannot be mi*ed&up+.
• A suitable scale representing the m*n&t"!e of the vector
uantity should be selected.
• %efore drawing a olygon of vectors, a reference or datum
direction should be defined.
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RAPHICAL SOLUTIONS CONT
• To derive a solution )i.e. a resultant+, proceed to draw thelines representing the vectors.
• The resultant is determined by measuring the magnitude
and direction of the line drawn from the st%t point to the
+&n&s point.