Spin City Slides Spin City
Centripetal vs. Centrifugal Forces
Why do things move in circles?
According to Newton's First Law, objects want to move in a straight line at a constant speed.
"Inertia is the tendency of an object to resist changes in its state of motion."
To make something turn, you must apply a force.
Centripetal Force
The "Center-Seeking" Force
A real force that pulls an object toward the center of a circular path.
Prevents the object from flying off in a straight line.
Examples: Gravity (planets), Tension (swinging a ball), Friction (car tires turning).
PATH OF MOTION
Directed Inward
Centrifugal Force
The "Center-Fleeing" Feeling
An apparent or "fictitious" force.
It is actually the result of inertia—your body wanting to keep going straight!
Feels like you are being pushed outward.
Sensation of Outward Push
Which is which?
Turning a Corner
The friction of tires pulling the car inward is Centripetal.
Salad Spinner
Water droplets being "thrown" to the outside edge is Centrifugal.
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Planetary Orbit
Gravity pulling a moon toward its planet is Centripetal.
Quick Comparison
Feature Centripetal Centrifugal Direction Toward the center Away from the center Type Real Force Apparent/Fictitious Cause External Push/Pull Inertia Meaning "Center-Seeking" "Center-Fleeing"
Force Faceoff Anchor Chart Force Faceoff
Centripetal vs. Centrifugal
Centripetal
"Center-Seeking"
A real physical force that pulls an object toward the center of its circular path, keeping it from flying off.
INWARD PULL
Real World Examples:
Tires on a track
Earth & Moon
Ball on string
Loop-the-loop
Centrifugal
"Center-Fleeing"
An apparent sensation of being pushed outward. It is caused by inertia, not an actual force.
OUTWARD FEELING
Real World Examples:
Salad spinner
Spin cycle
Merry-go-round
Lean in car turn
PRO TIP What's the difference?
If you are looking from outside the circle, you only see Centripetal Force pulling the object in. If you are inside the spinning object, you feel Centrifugal Force pushing you out!
Spin Comparison Venn Diagram Spin Comparison
Venn Diagram Activity
Student Name:
Date:
Mission Instructions
Compare and contrast Centripetal and Centrifugal forces. Use the word bank at the bottom to fill in the correct areas of the Venn Diagram. Focus on direction, physical reality, and common traits.
CENTRIPETAL
CENTRIFUGAL
Both Forces
Word & Phrase Bank
Inward direction
Apparent force
Requires circular path
"Real" force
Result of Inertia
Depends on mass
Outward feeling
Newton's Laws apply
"Center-Seeking"
"Center-Fleeing"
Involves acceleration
Friction/Gravity cause it
Spin City Curriculum Physics Unit: Circular Motion
Motion Mystery Worksheet Motion Mystery
PHYSICS LAB: CIRCULAR FORCES
Name:
Class:
1 Term Matching
Match the term on the left with its correct description on the right by writing the letter in the space provided.
Centripetal
A. The resistance of an object to change its state of motion.
Centrifugal
B. A center-seeking force that keeps objects in a curved path.
Inertia
C. An apparent force felt as an outward push away from center.
Tension
D. The center-seeking force provided by a rope or string.
Friction
E. The force that allows car tires to grip the road and turn.
2 Concept Completion
Apparent Centripetal Inertia Straight Line Outward Center Real Fictitious
1. Newton's First Law states that an object in motion will continue to move in a ______________________________ unless acted upon by an outside force.
2. A force that pulls an object toward the ____________________ of a circle is called centripetal force.
3. Centrifugal force is considered a ____________________ force because it is not actually pulling on the object; it is a feeling caused by ____________________.
4. While centripetal force pulls inward, the centrifugal "force" is felt as a push in the ____________________ direction.
5. Gravity acts as a ____________________ force to keep the planets in orbit around the Sun.
3 Identify the Force
Read each scenario. Decide if the description focuses on Centripetal or Centrifugal force.
A rider on a merry-go-round feels like they are being thrown off the side as it spins faster.
The string of a yoyo pulls the toy inward, preventing it from flying away during a "loop" trick.
In a washing machine, water is squeezed out of small holes in the spinning drum as the clothes are pushed against the walls.
A race car driver relies on the banking (tilt) of the track to help steer the car through a high-speed curve.
Whirlwind Wonders Reading Whirlwind Wonders
Physics Case Study: The Physics of the Spin
NAME:
DATE:
The Great Spin Debate
Imagine you are a passenger in a car that suddenly takes a sharp left turn. As the car swerves, you feel your body being shoved against the right-side door. If someone asked you what happened, you might say a force pushed you outward. In physics, this sensation is known as centrifugal force. However, according to scientists, that "force" doesn't actually exist as a physical push or pull.
To understand why, we have to look at Newton’s First Law of Motion: Inertia. This law states that an object in motion wants to stay in motion in a straight line. When the car turns left, your body—obeying the law of inertia—is trying to keep going straight. The car door is what actually moves into your path, hitting you and forcing you to turn with the vehicle.
The real star of the show in circular motion is centripetal force. The word "centripetal" comes from Latin words meaning "center-seeking." This is the real physical force that pulls an object toward the middle of its circular path. Without it, circular motion would be impossible.
Think of a planet orbiting the Sun. Gravity acts as the centripetal force, constantly pulling the planet inward. If gravity suddenly vanished, the planet wouldn't fly straight away from the Sun; it would fly off in a straight line tangent to its orbit, just like a ball would if you let go of a spinning string. Centrifugal is the feeling of being thrown out, but centripetal is the reality that keeps the spin alive.
Comprehension Check
1. According to the text, why is centrifugal force considered "fictitious" or not a real physical force?
A) It only happens in space.
B) It is actually the result of inertia resisting a change in motion.
C) It is too weak to be measured by scientists.
D) It only occurs when objects move in straight lines.
2. What does the Latin root of the word "centripetal" mean?
3. Using the example of the car turn, explain what the "door" represents in terms of force.
4. Based on the text, what would happen to a yoyo if the string (the centripetal force) snapped while it was being swung in a circle?
Spin City Literacy Series • Unit 4: Dynamics
Spin City Teacher Guide Spin City Solutions
Teacher Answer Key & Guide
Motion Mystery Worksheet
1. Term Matching
B - Centripetal
C - Centrifugal
A - Inertia
D - Tension
E - Friction
2. Concept Completion
1. Straight Line
2. Center
3. Fictitious / Apparent; Inertia
4. Outward
5. Centripetal / Real
3. Identify the Force
Merry-go-round sensation: Centrifugal
Yoyo string pull: Centripetal
Washing machine drum: Centrifugal
Race track banking: Centripetal
Whirlwind Wonders Reading
1. Multiple Choice:
B - It is actually the result of inertia resisting a change in motion.
2. Latin root meaning:
"Center-seeking"
3. The door representation:
The door provides the centripetal force. It physically pushes the person inward, forcing them to turn with the car instead of continuing in a straight line.
4. The snapped yoyo string:
The yoyo would fly off in a straight line (tangent to the circle), not directly away from the person. This is because its inertia wants to keep it moving in the direction it was going the instant the force disappeared.
Instructional Tips
Use the "Water in a Bucket" demonstration to show centripetal force in action.
Emphasize that centripetal is a label for a force (like gravity or friction), not a new type of magic force.
Correct the common misconception that centrifugal force pulls you out; explain it is the absence of an inward force to keep you turning.
