Examples of Free Body Diagram

Example 1: Draw the Free Body Diagram of mass M, as given below.

Solution:

Consider the Block A: When the mass M, is suspended using the two ropes, it weight(Mg) will start acting downward, which will cause tension in the ropes, let use name this tensions in the ropes as T1 and T2, then we can have our initial FBD as shown below:

Now, the tension in the strings will act such that, it will try to balance the weight of the ball (Mg), so we can resolve the tension T1 and T2, in there corresponding vertical and horizontal component.

Resolution of T1: Since T1 is at an angle β with the vertical, therefore the component of T1 along the vertical will become, T1cosβ and the component along the horizontal will become T1sinβ.

Resolution of T2: Since T1 is at an angle α with the vertical, therefore the component of T2 along the vertical will become, T2cosα and the component along the horizontal will become T2sinα.

Hence, we can draw the final FBD, will all the forces resolved along the vertical and horizontal components only, as below:

Example 2: A block is at rest on a platform with coefficient of friction μ is pulled by a force F acting at an angle θ, with the horizontal as show draw the free body diagram of the block.

Solution:

When the block is placed on the platform, its weight (Mg) will starting acting vertically downwards.

The weight acting downwards on the body will cause a normal force (F) from platform to act in the vertically upward direct.

Now when the force F will come into picture, since it is inclined at and angle θ, with the horizontal it will have to components one along the horizontal (Fcosθ) and the other along the vertical (Fsinθ)

Since there is no other force in the horizontal force in the horizontal direction other than Fcosθ, this will try to move to body on the platform which will cause the friction to act in the direction opposite to the direction of motion, hence the FBD of the body will look like:

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.