Have you ever felt like you're being pushed sideways in your seat when you're in a car going around a tight turn? Have you ever been on a roller coaster and felt heavier at the bottom of a curve and lighter at the top of a curve? What's going on in these scenarios?

Acceleration is a change in velocity. But velocity is a vector, so that could mean a change in magnitude (speed) or a change in direction. If an object is travelling in a circle at a constant speed, we say the object is in uniform circular motion. It's direction is changing as it turns so the object must be accelerating. This is centripetal acceleration, and it points towards the center of the circle.

But what causes a centripetal acceleration? We learned from Newton's 2nd law (F=ma) that a force applied to a mass will cause an acceleration.

So a centripetal force is what causes the centripetal acceleration of an object. Thinking about centripetal acceleration as being tied to a force might actually make things more intuitive. We'll learn about what creates a centripetal force and how to calculate it.

It's important to remember that a centripetal force is not a new "type" of force. It's just what we call the net force acting on an object which points towards the center of the circular path. The centripetal force could be a tension force, a normal force, a gravitational force, or the net force from multiple forces added together.

You may have also heard the phrase centrifugal force, is that the same thing? Centrifugal force is essentially the opposite of the centripetal force, and we'll learn how it's actually a "fictitious" force, meaning it's just an illusion.

So when you're driving a car around a tight turn and you feel a "force" pushing you to the side, or if you get in a carnival ride that spins and you stick to the wall, you may have thought a centrifugal force was pushing you outwards. But in reality, you were feeling a centripetal force pushing your body inwards and keeping you moving along that circular path.

Some of these sections are from the circular motion page as a review.

Multiple-Choice Questions

Answers

• Khan Academy - Centripetal force and acceleration intuition
• Michel van Biezen - Centripetal force
• Flipping Physics - Demonstrating Why Water Stays in a Bucket in a Vertical Circle
• Centripetal vs Centrifugal

• Khan Academy - Centripetal problem solving
• Khan Academy - Yo-yo in a vertical circle
• Khan Academy - Bowling ball in vertical loop
• Khan Academy - Angled centripetal force
• Organic Chemistry Tutor - Normal Force on a Hill, Centripetal Force, Roller Coaster

• What's the Most Realistic Artifiicial Gravity in Sci-Fi?

• Uniform circular motion and centripetal force

Other Resources

Have you ever felt like you're being pushed sideways in your seat when you're in a car going around a tight turn? Have you ever been on a roller coaster and felt heavier at the bottom of a curve and lighter at the top of a curve? What's going on in these scenarios?

Acceleration is a change in velocity. But velocity is a vector, so that could mean a change in magnitude (speed) or a change in direction. If an object is travelling in a circle at a constant speed, we say the object is in uniform circular motion. It's direction is changing as it turns so the object must be accelerating. This is centripetal acceleration, and it points towards the center of the circle.

But what causes a centripetal acceleration? We learned from Newton's 2nd law (F=ma) that a force applied to a mass will cause an acceleration.

So a centripetal force is what causes the centripetal acceleration of an object. Thinking about centripetal acceleration as being tied to a force might actually make things more intuitive. We'll learn about what creates a centripetal force and how to calculate it.

It's important to remember that a centripetal force is not a new "type" of force. It's just what we call the net force acting on an object which points towards the center of the circular path. The centripetal force could be a tension force, a normal force, a gravitational force, or the net force from multiple forces added together.

You may have also heard the phrase centrifugal force, is that the same thing? Centrifugal force is essentially the opposite of the centripetal force, and we'll learn how it's actually a "fictitious" force, meaning it's just an illusion.

So when you're driving a car around a tight turn and you feel a "force" pushing you to the side, or if you get in a carnival ride that spins and you stick to the wall, you may have thought a centrifugal force was pushing you outwards. But in reality, you were feeling a centripetal force pushing your body inwards and keeping you moving along that circular path.