#5: Understanding Circular Forces: A Beginner’s Guide

Rule #1: Keep it Simple Rule #2: Always Refer to Rule #1

Physics can be overwhelming, especially when you're faced with diagrams filled with circles and triangles. But don’t worry—this guide breaks circular motion down into its simplest components.

n circular motion concepts in a straightforward way, perfect for your first encounter with physics.

Tangential Velocity: Moving Along the Edge of a Circle

Let’s start with what you already know: v = d / t Where:

• v is velocity

• d is distance

• t is time

In circular motion:

• The time to complete one full circle is called the Period (T).

• The distance covered in one full circle is the Circumference (2πr).

Substituting these into the formula gives us: v = 2πr / T

Here’s a crucial point: The tangential velocity is always perpendicular to the centripetal acceleration. This perpendicular relationship is what allows an object to maintain its circular path.

Centripetal Acceleration: Pulling Toward the Center

For now, use the formula: ac = v² / r

• ac is centripetal acceleration

• v is tangential velocity

• r is the radius of the circle

What does “centripetal” mean? Simply put, it means “toward the center.” Every force keeping an object moving in a circle is directed inward.

Important Note: Avoid using the term “centrifugal.” It doesn’t apply to the phenomena you’re studying here.

If we substitute v = 2πr / T into ac = v² / r, we get: ac = 4π²r / T²

Summing Forces in Circular Motion

Dealing with forces is all about direction. Follow these steps:

1. Draw a Free Body Diagram: Include the force of gravity and the force providing the circular motion (e.g., tension or normal force).

2. Understand the Direction:

   • At the bottom of the circle, the centripetal force points up (positive).

   • At the top of the circle, the centripetal force points down (negative).

3. Set Up Your Equations (Vegas Chart): Sum the tension or normal force and the force of gravity. Set this equal to the centripetal force. Don’t forget to use the appropriate signs for upward and downward forces.

Final Tips for Success

• Focus on these foundational concepts before diving into complex derivations.

• Always start with the basics: draw diagrams, identify forces, and use proper signs.

  
  

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