Back To Course

AP Physics 1: Exam Prep13 chapters | 143 lessons | 6 flashcard sets

Instructor:
*Matthew Bergstresser*

When learning about forces and motion, it is helpful to conduct a hands-on activity. In this lesson, we will do an activity relating force and motion by analyzing a mass that is swung in a horizontal circle.

The following activity is designed to show the relation between force and motion by determining the value of a mass which is moving at constant speed in a circular path.

- A thin plastic tube
- 1 meter of nearly massless string
- A rubber stopper of unknown mass
- An assortment of metal washers totaling 1200 g
- A mass scale
- A timer
- Red tape

1. Slide string through thin plastic tube and securely attach rubber mass to string at one end.

2. Put piece of red tape on string 0.5 m from rubber mass.

3. Slide plastic tube to the bottom of the red tape and put another piece of red tape on the string at the bottom of the plastic tube.

4. Attach 0.5 g of washers to other end of string.

5. Hold on to plastic tube and swing rubber mass around your head so that the pieces of red tape stay at the top and bottom of the red tube.

6. When constant velocity has been reached (both pieces of red tape aren't moving), start the stopwatch and count 10 revolutions. Stop the stopwatch at 10 revolutions and slowly bring the rubber mass to a stop.

7. Weigh the washers.

8. Repeat steps 5-8 until you have 5 different masses of washers and a maximum washer mass of at least 1000 g.

The measurements we have to take are the mass of the washers for each new set of washers, and the time it took for 10 revolutions. The data for this is shown in Data Table 1.

The hanging washers put tension on the string. This tension force is exerted through the entire string and acts as the **centripetal force**, which is the force acting towards the center of the circle, allowing the rubber stopper to move in a circular path. Even though the rubber stopper moves with constant speed in its circular path, it is accelerating towards the center of the circle. This is known as a **centripetal acceleration**. This acceleration demonstrates that there is an unbalanced force on the mass, and that force is the tension in the string.

Gravity is also acting on the mass, but it is in the vertical direction and not in the line of the centripetal force. Technically, the mass cannot be moving perfectly horizontally because there has to be a force to counter the gravitational force. The string is slightly angled to give a small vertical component of tension to counter the weight of the mass. We can ignore that here because there is no vertical acceleration.

The graph of the square of the speed (v2) vs centripetal force (weight of washers) gives us the ratio of the radius of the circle to the mass of the rubber stopper, which is the slope of the best-fit line through the data.

The speed equation is

*v*= speed in m/s*d*is distance the rubber stopper moves in its path in 1 revolution in meters*R*is the radius of the circle in meters*t*is the time for 1 revolution in seconds (each time in the data table divided by 10 because of the 10 revolutions)

The weight of the washers is the mass of the washers times the acceleration due to gravity (9.8 m/s2).

This information is tabulated in Data Table 2.

We will graph this data, and draw a best-fit line through it.

We can see from the graph that the data plotted is linear. In fact, the slope of the line is given in the equation of the line, which is 0.633 m2/s2 / N. Let's analyze what these units reduce to.

The equation for centripetal force is

which can be rearranged to solve for v2/Fc.

We have the ratio of R/m from the slope of the best fit line, and we know the radius of the circle. This means we can determine the mass of the stopper.

Finally, we need to weigh the stopper, and compare the masses. The stopper weighs 0.692 kg on the scale.

The percent error of our stopper mass is

This percent error is very acceptable in an experiment where reaction time using a stopwatch is part of the data gathering. Other sources of error are the assumption that the string is massless, the circular path the rubber stopper went through might not have been exactly circular, and the string attached to the stopper wasn't perfectly horizontal.

The purpose of this experiment was to determine the mass of a stopper on the end of a string moving in a circular path. Anytime something moves in a circular path it experiences a **centripetal acceleration**, which is an acceleration towards the center of the circular path. An unbalanced force provides this acceleration, and it is called the **centripetal force**.

We had a string passing through a plastic tube. On one end of the string was the rubber stopper, and on the other end, a mass of washers. The weight of the washers, which was increased with each trial, provided the tension in the string, and thus the centripetal force.

The plot of the square of the constant speed of the mass versus the centripetal force gave us a straight line with the slope having dimensions of v2/N. Using the centripetal force equation

along with the slope of the line, we were able to determine the mass of the stopper.

To unlock this lesson you must be a Study.com Member.

Create your account

Are you a student or a teacher?

Already a member? Log In

BackWhat teachers are saying about Study.com

Already registered? Login here for access

Did you know… We have over 160 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

You are viewing lesson
Lesson
11 in chapter 4 of the course:

Back To Course

AP Physics 1: Exam Prep13 chapters | 143 lessons | 6 flashcard sets

- Newton's First Law of Motion: Examples of the Effect of Force on Motion 8:25
- Distinguishing Between Inertia and Mass 6:45
- Mass and Weight: Differences and Calculations 5:44
- State of Motion and Velocity 4:40
- Force: Definition and Types 7:02
- Forces: Balanced and Unbalanced 5:50
- Free-Body Diagrams 4:34
- Solving Mathematical Representations of Free-Body Diagrams
- How to Use Free-Body Diagrams to Solve Motion Problems 6:58
- Net Force: Definition and Calculations 6:16
- Force & Motion: Physics Lab
- Determining the Acceleration of an Object 8:35
- Action and Reaction Forces: Law & Examples 8:15
- Determining the Individual Forces Acting Upon an Object 5:41
- Implications of Mechanics on Objects 6:53
- Air Resistance and Free Fall 8:27
- Newton's Third Law of Motion: Examples of the Relationship Between Two Forces 4:24
- Newton's Laws and Weight, Mass & Gravity 8:14
- Identifying Action and Reaction Force Pairs 8:12
- The Normal Force: Definition and Examples 6:21
- Friction: Definition and Types 4:15
- Inclined Planes in Physics: Definition, Facts, and Examples 6:56
- Go to AP Physics 1: Newton's Laws

- AFOQT Information Guide
- ACT Information Guide
- Computer Science 335: Mobile Forensics
- Electricity, Physics & Engineering Lesson Plans
- Teaching Economics Lesson Plans
- FTCE Middle Grades Math: Connecting Math Concepts
- Social Justice Goals in Social Work
- Developmental Abnormalities
- Overview of Human Growth & Development
- ACT Informational Resources
- AFOQT Prep Product Comparison
- ACT Prep Product Comparison
- CGAP Prep Product Comparison
- CPCE Prep Product Comparison
- CCXP Prep Product Comparison
- CNE Prep Product Comparison
- IAAP CAP Prep Product Comparison

- What Are the 5 Ws in Writing? - Uses & Examples
- Phenol: Preparation & Reactions
- What is a Color Wheel? - Definition & Types
- What Are Abbreviations? - Meaning, Types & Examples
- Zentangle Lesson Plan for High School
- West Side Story Discussion Questions
- Fireboat: The Heroic Adventures of the John J. Harvey Activities
- Quiz & Worksheet - Solvay Process
- Quiz & Worksheet - Acetone Reactions
- Quiz & Worksheet - Themes in A Raisin in the Sun
- Quiz & Worksheet - Act & Rule Utilitarianism Comparison
- Analytical & Non-Euclidean Geometry Flashcards
- Flashcards - Measurement & Experimental Design
- Algebra 1 Worksheets
- Reading Comprehension | A Guide for Teaching Reading

- Common Core ELA - Informational Text Grades 9-10: Standards
- CSET Science Subtest I - General Science (215): Practice & Study Guide
- Introduction to Psychology: Certificate Program
- CAHSEE Math Exam: Tutoring Solution
- Accuplacer Math: Quantitative Reasoning, Algebra, and Statistics Placement Test Study Guide
- AP Psychology: Learning & Conditioning Lesson Plans
- AP Psychology: Motivation in Psychology Lesson Plans
- Quiz & Worksheet - Legal Adolescence
- Quiz & Worksheet - At-Risk Youth Statistics
- Quiz & Worksheet - 1970s Arts & Culture in the US
- Quiz & Worksheet - Woodrow Wilson's New Freedom
- Quiz & Worksheet - Tips for Finding Colleges With the Major You Want

- What is the 19th Amendment? - Definition, Summary & Date Ratified
- Comparing Two Sets of Money
- Georgia Physical Science Standards
- Reading Comprehension Lesson Plan
- TExES PPR Test Registration Information
- Scientific Method Lesson Plan
- National Science Standards for Middle School
- Mitosis Lesson Plan
- Halloween Math Activities
- Idaho Science Standards for 3rd Grade
- Roaring 20s Lesson Plan
- Understanding TELPAS Scores

- Tech and Engineering - Videos
- Tech and Engineering - Quizzes
- Tech and Engineering - Questions & Answers

Browse by subject