Free Body Diagrams(Internal & External Forces)

-Define the system,Sometimes called a force diagram.-Sketch the system.-Used by engineers & physicists to analyze the forces & moments acting on a body.-Show the interactions with forces & torques.-To analyze a problem in statics or dynamics.-Show the relative magnitude & directions of all forces acting on an object.

Some Examples.......

Problem 1:

Take a my Iphone 5 & drop it. Diagram the forces acting on the book.

In this diagram,

there arenormalAndgravitationalforces on myIphone 5.

Problem 2:

An egg is free-falling from a nest in a tree. Neglect air resistance. Draw a free-body diagram showing the forces involved.

Gravity is the only force acting on the egg as it falls.

Problem 3:

A rightward force is applied to my Iphone 5 in order to move it across a desk. Consider frictional forces. Neglect air resistance. Construct a free-body diagram. Let’s see what this one looks like.

Note the applied force arrow pointing to the right. Notice how friction force points in the opposite direction. Finally, there is still gravity and normal forces involved.

Procedure for Drawing a FBD

1. Draw Outlined Shape

2. Show All Forces and Couple Moments

3. Identify Each Loading and Give Dimensions

Draw the free-body diagram of the uniform

beam.The beam has a mass of 100kg.

Support Reactions If a support prevents the translation of a body in a given direction, then a force is developed on the body in that direction.

If rotation is prevented, a couple moment is exerted on the body.

Forces on an ObjectExternal and internal forces can act on a

rigid body For FBD, internal forces act between

particles which are contained within the boundary of the FBD, are not represented

Particles outside this boundary exert external forces on the system

Draw the free-body diagram of the unloaded platform that is suspended off the edge of the oil rig. The platform has a mass of 200 Kg.

Two- and Three-Force Members

Some objects can be two or three force members.

Two-Force Members

When forces are applied at only two points on a member, the member is called a two-force member

Only force magnitude must be determined

Three-Force Members

When subjected to three forces, the forces are concurrent or parallel

Thanks all of You....Have a nice day...

**********THE END**********

This presentation is prepared by

SHAHRIAR MUJTAHID HOSSAIN 10.01.03.062