Conditions Of Equilibrium Of A Body

Done By : Doaa Al Mahdawi Salah Al Sary

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محمود درويش

ForcesMain Objectives: •To define the Force.•To characterize the Force.•To distinguish between the different types of the Forces.•To deduce the conditions of equilibrium of two forces.

Definition of the Force:

A force is a mechanical action that may set a body in motion or modify its motion or modify its shape.

Pulling

Characteristics of Force:

•Its point of application: is the center of gravity of the body or point of contact.

•Its line of action: vertical, horizontal or oblique.

•Its direction: (upward- downward), (to the right, to the left), (upward to the right, downward to the right, upward to the left, downward to the left).

•Magnitude: Its numerical value in the SI unit Newton (N)

Measurement of Force:•A force is measured using spring balance.

•Its SI unit is Newton symbolized by N.

• A force is represented by force vector (convenient scale must be chosen to draw F).

Types of Force:

•Forces acting from a distance ex: magnetic force, electric force and gravitational force.

•Contact force ex: normal, pushing pulling, tension…

Particular Forces:

The weight:•The weight of a body is force acting from a distance

exerted by the earth on the object. It is also called the force of gravity.

The characteristics of weight:

•Its point of application: the center of gravity of the body.

•Its line of action: vertical.•Its direction: downward.•Magnitude: W = m × g.

Normal: It is a force exerted by a surface on a body. It is a contact force.

To find the characteristics of normal:

•Its point of application: point of contact.

•Its line of action: vertical

•Its direction: upward.

•Magnitude: ------

Tension: It is a force exerted by a spring or string on a body. It is a contact force.

To find the characteristics of tension:

•Its point of application: point of contact.

•Its line of action: vertical

•Its direction: upward

•Magnitude: T= k × ∆x

Force of friction: It is a force due to the sliding (motion) of a body. It is a contact force.

To find the characteristics of friction:

•Its point of application: point of contact.•Its line of action: along the line of motion.•Its direction: opposite to the motion.•Magnitude : -----

Equilibrium of a body:

Equilibrium of a body:

When a body is in equilibrium then the two forces have:

•Same line of action•Opposite direction•Same magnitude

Exercise I:

( S)

A box (S) of mass 1kg is suspended to the free end of a spring as shown in the figure.Take g=10N/Kg.

•Name the forces acting on solid (S).

•Calculate the weight of (S).

•Deduce the following characteristics of a force exerted by a spring on (S): a. Line of action . b. Direction . c. Magnitude .

DONE