### Circular Forces

Circular Forces Lab

Purpose:

In this activity you will be using investigating the factors that affect the force needed to hold an object in circular motion.  You will be changing the mass of the object moving in a circle, the speed of the object moving in a circle and the radius of the circle.

Part 1: Virtual Test of Mass and Force

1. For the first few parts of the lab you will be using a simulation program that can be found here.

2. Leave the radius at 1.5 meters for this part of the lab don't change the speed but leave it at the random speed that was generated when you opened the program.

3. Set the mass at 1.5 kg and hit the start button.  You do not need to time anything, but instead, take a look at the reading on the force probe and make a good estimate of the force holding the disk in circular motion.

4. Make a data table that will hold 8 different masses and the force that is required to hold them in this circle at this speed.

5. After you collect all your data, make a graph with your independent variable on the x-axis and the dependent variable on the y-axis.

6. Copy the graph and equation into your lab book.  And give a quick conclusion about how the mass affects the force.

Part 2: Virtual Test of Radius and Force

1. For this part of the lab, set the mass at 800 grams and don't change the speed but leave it at the same random speed that was generated when you opened the program.

2. Set the radius at 1.5 m and hit the start button.  You do not need to time anything, but instead, take a look at the reading on the force probe and make a good estimate of the force holding the disk in circular motion.

3. Make a data table that will hold 8 different radii and the force that is required to hold them in the circle of this size.

4. After you collect all your data, make a graph with your independent variable on the x-axis and the dependent variable on the y-axis.

5. Copy the graph and equation into your lab book.  And give a quick conclusion about how the radius affects the force.

Part 3: Virtual Test of Speed and Force

1. For this part of the lab, set the mass at 800 grams and the radius to 1.5 m.

2. Hit the start button.

3. Once the disk is in motion get ready to time it for enough revolutions that you can get good data to calculate speed.

4. Use your revolutions times your circumference divided by your time to determine the speed of the disk.

5. Take a look at the reading on the force probe and make a good estimate of the force holding the disk in circular motion.

6. Make a data table that will hold 5 different trials.  Each trial should include the number of revolutions you timed, the time for those revolutions, the speed and  the force that is required to hold the disk in the circle.

7. After each trial generate another random speed.

8. After you collect all your data, make a graph with your independent variable on the x-axis and the dependent variable on the y-axis.

9. Copy the graph and equation into your lab book.  And give a quick conclusion about how the radius affects the force.

Part 4: Live test of speed and force.

1. Lab Setup for the live part of the experiment:

2. Set up your data table to look like the one given below:

 # of washers mass (kg) Force (N) Time (s) speed (m/s) make rows for all groups in your class.

3. Set the radius of the stopper to 75 cm.  Place a piece of masking tape a centimeter or two below the bottom of the glass tube.

4. Get the mass of 10 washers, record the mass in kilograms and then calculate the force of gravity they will be applying to the string.

5. Start the stopper moving in a circle and adjust the speed of the stopper so that the masking tape is a centimeter below the bottom of the glass tube.   See Example Below

6. Continue to have the stopper move at that speed and time how long it takes the stopper to make 30 revolutions.  To access a stopwatch, click here.

7. Calculate the speed of the stopper.

8. Repeat the procedure for 15 washers, 20 washers, 25 washers, 30 washers, and 5 washers.

9. When you create your graph for speed vs force make sure you include a zero, zero point on your graph.  If you need help with curve fitting your graph see here.

10. Make sure you write out an equation to relate the speed of the stopper the force on the washers.

Things needed in Lab book:

1. Purpose

2. Data tables, graphs and equations for all virtual parts of the lab.

3. A sentence or two of conclusion for each of the parts of the lab.

4. A picture of lab set up for the live part of the lab.

5. Data table with all the data your class collected.

6. One Sample calculation for determining the speed from the revolutions, time and radius.

7. A graph for the class part of the lab with all the things a good graph should contain

8. The mathematical equation for the graph.

9. Two good sources of error present in the lab and a way to correct these errors.
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