Poligon Kecepatan UII

Summary

This video explains how to analyze the velocity of points in a four-bar mechanism using graphical methods. It details the process of determining the velocity of point A, the piston (point B), and the relative motion between points A and B. The video illustrates the use of velocity polygons to represent these velocities, calculating them using angular velocities and distances. The solution method combines both absolute and relative velocity analyses to find the required velocities in a mechanical system, making complex kinematic relationships more accessible through visualization.

Takeaways

• 😀 The script explains the graphical method used to calculate the velocity of points in a mechanical system involving multiple interconnected rods.
• 😀 Point A's velocity is determined based on the angular velocity of rod 2 and its radius, with the velocity being perpendicular to the direction of rod 2.
• 😀 The magnitude of velocity at point A is calculated as omega2 multiplied by R2, where omega2 is the angular velocity of rod 2 and R2 is its radius.
• 😀 A velocity polygon is used to visually represent the speed and direction of the moving points, with the scale of the diagram helping to relate theoretical values to actual measurements.
• 😀 Point B's velocity is initially unknown but can be found by analyzing the relationship between rods 4 and 1. The direction of velocity is perpendicular to rod 4.
• 😀 The velocity at point B is derived by using the graphical method, combining the known velocities at points A and B relative to each other.
• 😀 The relative velocity between points B and A (VBA) is calculated by considering the movement of point B as if point A is stationary.
• 😀 The graphical method provides a way to combine velocities at different points, with the final velocity of point B being the sum of the velocities at points A and B relative to A.
• 😀 The direction of the velocity at point B is horizontal, reflecting the movement of the piston, which is related to the movement of rod 4.
• 😀 Once the velocity of point B (VB) is determined graphically, its actual magnitude is calculated by multiplying the length of the velocity vector by the scale used in the diagram.

Q & A

What is the primary goal of the analysis in this script?

The primary goal is to analyze and determine the velocities of various points (A and B) in a four-bar linkage system using graphical methods and poligon velocity diagrams.

How is the velocity of point A calculated?

The velocity of point A is calculated using the formula Va = ω2 * R2, where ω2 is the angular velocity of the second link and R2 is the radius (or length) of the second link.

What is the direction of the velocity of point A relative to link 2?

The velocity of point A is perpendicular (normal) to link 2 and is directed to the left, as the rotation of link 2 is counterclockwise (to the left).

What does the term 'poligon kecepatan' refer to?

'Poligon kecepatan' refers to a velocity polygon, a graphical tool used to represent and calculate the velocities of different points in a mechanism by drawing vectors proportional to the calculated velocities.

How is the velocity of point B determined?

The velocity of point B is determined using the method of relative velocities. First, the velocity of point B relative to point A (Vba) is calculated, and then the total velocity of point B (VB) is found by adding Va and Vba, i.e., VB = Va + Vba.

What is the significance of the direction of velocity at point B?

The direction of the velocity of point B is perpendicular to link 4, which corresponds to the horizontal motion of the piston, moving either to the left or right.

Why is the velocity at point A represented in a velocity polygon?

The velocity at point A is represented in a velocity polygon to visually represent the magnitude and direction of the velocity, which is crucial for understanding the kinematics of the system.

What is the role of the four-bar linkage in this analysis?

The four-bar linkage serves as the mechanical system being analyzed, with various bars (links) rotating and moving in relation to each other, which determines the velocity of different points like A and B.

What does the term 'kecepatan relatif B terhadap A' mean?

'Kecepatan relatif B terhadap A' means the relative velocity of point B with respect to point A, which is calculated assuming point A is stationary, and then the velocity of point B is determined based on the rotation of the linkage.

How are the velocities of points A and B visually represented in the process?

The velocities of points A and B are visually represented in a velocity polygon where vectors proportional to the velocity magnitudes are drawn. The vectors are connected to represent the directions and relative relationships between the velocities of the points.