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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.