Free Body Diagram in Physics
Free Body Diagram in physics can be made for several physical phenomena such as a body in motion is subjected to some load. In this section we will discuss FBD for following types
- Free Body Diagram of Circular Motion
- Free Body Diagram of Frictional Force
- Free Body Diagram of Friction on Inclined Plane
Free Body Diagram of Circular Motion
Consider a ball initially at the bottom of a circular path, let’s use try to understand the Free Body Diagram of the when it move on the circular path with a velocity of v. In this section we will learn how the different forces are acting on different positions of the ball in the circular path.
Free Body Diagram of the Ball at Rest
When the ball will be at rest it will have a its weight acting downwards (W = mg), which will cause a Normal Force (N) from the surface to act on the object.
FBD of the ball at rest
Free Body Diagram of Ball at the Bottom of the Path when moving with a velocity of v:
We know every object moving on a circular path with a velocity v of a circular path experiences a Centrifugal Force away from the center. So when the ball will start moving it will experience Centrifugal Force given as
Cf = mv2/r
where,
- m is the mass of the ball,
- v is the velocity with which the ball is moving and,
- r is the radius of the circular path,
Hence the free body diagram will look like as follows:
FBD of moving ball at bottom
Free Body Diagram of the Ball at the Middle of the Path when Moving with a Velocity of v:
We know every object moving on a circular path with a velocity v of a circular path experiences a Centrifugal Force away from the center, so when the ball will start moving and reach the horizontal position as shown, it will experience a forces (Centrifugal Force Cf = mv2 / r) , which will cause a Normal Force(N) to come into action towards the center and weight will always be acting vertically downwards.
Hence the free body diagram will look like:
FBD of moving ball in middle
Free Body Diagram of the ball at the Topmost Position of the path when moving with a velocity of v:
When the ball will reach the highest position of the circular path, it will have its weight (W = mg) acting downwards, and Centrifugal Force (Cf = mv2 / r), which will cause a Normal Force (N) to act towards the center of the path.
Hence the Free Body Diagram can be shown as:
FBD of moving ball at top
Free Body Diagram for Frictional Force
When a body is placed on a plane, instantaneously its Weight (W=mg) will start acting vertically downwards which will cause a Normal Force (N) from the ground to come into action. Now when the body is at rest the friction action of the body will be zero, but as soon as the body starts moving a friction (f = μN) will start acting opposite to the direction of motion.
Hence the Free Body Diagram of block placed on plane with coefficient of friction (μ), will look like as shown below where, [Tex]0 \leq f \leqslant \mu N [/Tex], is applicable
FBD for Frictional force
Free Body Diagram of Inclined Friction
Consider a body of mass m placed on an inclined plane, it weight will start acting vertically downwards, but friction and Normal Forces will act along and perpendicular to the inclined surface, so will consider a coordinate system where x axis is parallel to the inclined surface and y-axis is perpendicular to it.
FBD of Inclined Friction
Since inclined angle is making a θ angle with the horizontal, the component of weight parallel to inclined will make a 90 – θ angle with the vertical, hence the components of weight can be resolved as Wp = mgcosθ and W|| = mgsinθ. See the figure:
Free Body Diagram of Inclined Friction with Co-ordinate system
After, Resolution of Weight Component along perpendicular and parallel to the inclined plane is shown below:
FBD of Inclined Friction after Resolution
Now the normal force (N) will start acting perpendicular to the surface of the inclined and a friction (f = μN) will act parallel to the surface of the inclined. Hence the free body diagram will look like:
FBD on the inclined plane with friction
Free Body Diagram
Free Body Diagram often called FBD is a way of representing all the forces acting on a body at a particular instant in a simpler form. It enables the calculation of the net force acting on the body and its direction of motion by making a symbolic diagram of all the forces acting on a body.
In this article, we will learn in detail about the Free Body Diagram, what are its features, how to make it, and solve some examples based on it.
Table of Content
- What is Free Body Diagram?
- How to Make Free Body Diagram
- Free Body Diagram in Physics
- Significance of Free Body Diagram
- Examples of Free Body Diagram