Civil EngineeringDepartment (GIA)

Wel-Comes YOU.....

HJD Institute Of Technical

Education And Research-Kera

PRESENTING BY :-

1. Patel Ashish C.

2. Jethwa Kashyapsinh M.

3. Bhatti Anishamhed A.

4. Ramjiyani Dhaval J.

5. Mitesh

Definition :-

Coplanar Non-concurrent Forces.

It means that the forces which acts in a single plane but at a different point.

Moment Of A Force :-The moment of a force is equal to the product of the force and the perpendicular distance of line of action of force from the point about which the moment is required.

M = P x X

Here, M = moment P = Force X = Perpendicular distance between the line of action of force and the point about which moment is required.

Unit of moment is N.m. Or kN. m.

Examples of moment :-

I. To tight the nut by spannerII. To open or close the door

Sign for moment :- Generally, clockwise moment is taken

as positive and anticlockwise moment is taken as negative.

Couple:-

To equal and opposite forces whose lines of action are different form a couple.

Resultant or net force of couple is zero. Hence, couple acting on a body do not create any translatory motion of the body.

Couple produces only rotational motion of the body.

Types of couple :-

There are two types of couple.

I. Clockwise coupleII. Anticlockwise couple

a = arm of couple.

Clockwise couple

It rotates the body in clockwise direction.

It is taken as positive.

It is taken as negative.

Anticlockwise couple

It rotates the body in anticlockwise direction.

Arm of couple :-

The perpendicular distance between the lines of action of two forces forming couple is know as the arm of couple.

Moment of couple :-

Moment of couple = Forces x arm of couple

M = P x a

unit of couple is N.M. Or KN.M

Example of couple are :-

I. Forces applied to the key of a lock, while locking or unlocking it.

II. Forces applied on the steering wheel of a car by two hands to steer the car towards left or right.

III.To open or close wheel valve of a water supply pipe line.

CHARACTERISTICS OF A COUPLE :-

I. The algebric sum of the forces, forming the

couple is zero.

II. The algebric sum of the moment of the

forces, forming the couple, about any point

is the same and equal to the moment of the

couple itself.

Moment of couple M = P.a

Now, taking moment @ 0,

III. A couple cannot be balanced by a single

force, but can be balanced only by a couple,

but of opposite nature.

DIFFRENCE:-MOMENT

I. Moment = Force x Perpendicular distance M = P.x II. It is produced by a single force not passing

through C.G. of the body.III. The force move the body in the direction

of force and rotate the body.IV. To balance the force causing moment,

equal and opposite forces is required.V. For example. - To tight the nut by spanner. - TO open or close the door.

COUPLE

I. Two equal and opposite forces whose lines of action are different form a couple.

II. It is produced by two equal and opposite parallel, non-collinear forces.

III. Resultant force of couple is zero. Hence, body does not move, but rotate only.

IV. Couple can not be balance by a single force. It can be balance by a couple only.

V. For example, - To rotate key in the lock. - To open or close the wheel valve of line. - To rotate the steering while of car.

CONDITION OF EQUILIBRIUM FOR COPLANER NON – CONCURRENT FORCES:-

If the body is acted upon by a number of co-planar non-concurrent forces. It may have one of the following stats:

I. The body may move in any one direction.

II. The body may rotate about itself without moving.

III. The body may move in any one direction, and at the same time it may also rotate about itself.

IV. The body may be completely at rest.

EXAMPLE :- ABCD is a square of 5 m. side forces of 100 N, 250 N, 150 N and 300 N, act along BA,DA, DC, BC, respectively. Find the algebric sum of the moments of all the forces about the centrePoint of thesquare.