AP Physics 2 Unit 4 Lab

Elisa Alvarado, Sarah Cratem, Ryan Partain, Julia Reidy

Mr. Thomas

AP Physics 2 cmod

13 December 2015

Unit 4: Charged Particle Interaction Model Lab Report

Objective: To determine the mathematical and graphical relationship between electrostatic force and distance between a neutral and charged object, and to determine the graphical and mathematical relationship between electric force, distance between a neutral particle and a charged particle (r), and the distance traveled by the neutral particle (x).

Apparatus:

Trig Relationships and Force Diagram:

Procedures:

1. Place physics stand 1 meter apart and place the meter stick on top of the stands. Tape the meter stick to the stands. Apply a charge to one balloon by rubbing it against your hair.
2. Tie the strings to the stands and tie the one balloon to each string
3. Separate the charged balloon from the uncharged one until the uncharged one is unaffected by the charge and is at rest directly between the stands.
4. Bring the charged balloon closer to the neutral balloon until the neutral balloon moves and measure the distance between the two and the distance the uncharged balloon was displaced.
5. Repeat the 4th step 8 times and be sure the same increments are used for each trial. Record the space between each of the balloons and how much each balloon is displaced during each trial.
6. Calculate the electric force using net forces and trigonometry as shown in the diagrams above.

Data Tables:

Graphs:

This shows an inverse relationship between delta x and r. To linearize this graph we must take the inverse squared of the quantity r.

displacement vs. 1/r^2

This graph shows a linear relationship between displacement and 1/r^2, as represented by the equation Δx = (1.53 x 10-4m3)/r2.

This graph shows an inverse relationship between electrostatic force and distance between the two balloons. To linearize this relationship we must take the inverse squared of the quantity r.

This graph demonstrates a linear relationship between electrostatic force and the inverse squared of r, represented by the equation Fe= (7.768x10^-6 Nm^2)(1/r^2).

Conclusion:

Our first graph showed an inversely proportional relationship between the change in position of balloon 2 and the distance between the two balloons. To linear use this graph we took the inverse quaked of the quality r. This left us with the relationship of delta x is proportional to 1/r^2.  Since electric force follows this same relationship, we can infer that Fe is proportional to 1/r^2. To determine the electric force we used the force diagram above. From this force diagram we used trigonometry to find the equation Fe = mgtanθ. When you solve for theta using trigonometry the new finalized equation comes out to be Fe=mgtan(Δx/0.2). M is the mass and g is the gravitational constant. To make a general equation to relate the electrostatic force to 1/r^2 we added in a constant k to represent Coulomb's constant. So that Fe = k/r^2. Since the force and the charges show the same proportional relationship to one another we added in Fe=(kq1q2)/r^2. The slope from out linearized graph gave us the number 7.7e-6Nm^2  which represents the product of Coulomb's constant and the charges. ( 7.7e-6Nm^2 =kq1q2)

Error in this lab could have resulted from human errors from measuring the exact distances the objects moved. There could have also been error with the charge of the balloon being greater or lesser at some time.