Applications of Centripetal Force

Overview

This lesson turns the centripetal-force model into problem solving. The main skill is identifying which real force, or combination of forces, is acting towards the centre of the circular path.

What You Need to Know

• Centripetal force is not a new force; it is the inward resultant force needed for circular motion.
• The inward force might come from tension, friction, gravity, contact forces, or a combination of forces.
• If the available inward force is too small, the object cannot follow the circular path.
• Clear diagrams are often the difference between a correct equation and a wrong one.

How to Work Through It

1. For each situation, mark the centre of the circular path before drawing forces.
2. Resolve or combine forces to find the inward resultant force.
3. Set the inward resultant equal to mv^2 / r or mr omega^2.
4. Interpret the answer in words, especially when a limiting speed or radius is involved.

Check Your Understanding

• What provides the centripetal force for an object moving in a horizontal circle on a string?
• How would the required force change if the speed doubled?
• What does it mean physically if the calculated force is larger than the available force?

Common Mistakes

• Writing “centripetal force” as the source of the force instead of naming the real interaction.
• Assuming every circular-motion example has the same force diagram.
• Substituting diameter where the equation needs radius.

Next Steps

• Review any example where the force diagram was difficult before moving on.
• Keep the idea of restoring or inward resultant force in mind for simple harmonic motion.