11.3 Uniform Motion & Electric Fields Part 2

Lab: Positive Particle Moves Parallel to the Electric Field This lab consists of four parts. In Part A, you will examine the motion of a positively charged particle when it initially moves parallel to the electric field.  In Part B you will examine the motion of a positively charged particle when it initially moves perpendicularly to the electric field.  In Part C you will examine how a negatively charged particle will move when it starts perpendicular to the electric field.  Finally, in Part D you will try to get the particle to move with uniform motion.

 

Purpose - Part A

 

In this part of the lab activity, you will use a computer simulation to collect data enabling you to answer the following questions:

• How does a positive particle move when the direction of its initial velocity is opposite to the direction of the electric field?
  
• How can this motion be explained using physics principles?

Procedure

 

Step 1: Open the Particle in an Electric Field simulation, and enter the following settings:

• Enter a value of 75 V/m for the magnitude of the electric field in the electric field display panel and set the direction of the electric field to 270°.   Note that the electric field vector is shown as a large, blue arrow.  The small, blue arrows indicate that the field has the same value at all locations on the screen.
  
  
• Enter a value of 150 m/s for the magnitude of the initial velocity in the velocity display panel and set the direction of the initial velocity to 90° using the drop-down menu in the velocity display panel.   The velocity vector is shown as a red arrow.
  

• Set the particle's charge and mass to + 2.0 C and 3.0 kg, respectively.

• Leave the particle on the x-axis.

• Note that if you use "rewind", you can return to these initial settings at any time during this lab activity. However, if you use "reset", you will have to re-enter all these initial settings.

If these settings have been applied, the screen should look like this:

 

 

Step 2: Given these initial conditions, make a prediction as to how you think the particle will move if it is released.  Press the "play" button to confirm your prediction.

 

Step 3: Use "rewind" to return to the initial settings.  Repeat the previous step, but use "pause" to stop the motion at the instant the particle reaches its highest point.  Use "Simulation Data" to see the information about the elapsed time, Δ t , the x and y components of the acceleration ( x , y ), and the x and y components of the displacement ( d _x , d _y ) from the start of the motion.

 

Step 4:   Collect the following data:

 

elapsed time   Δ t = ________ s

 

charge    q = ____________ C

mass    m = ___________ kg

Express the remaining values in terms of x and y components:

 

electric field    = ___________V/m

acceleration   ( a _x , a _y ) = ___________m/s ²

initial velocity   ( v _{i x} , v _{i y} ) = (0, 150) m/s

final velocity   ( v _{f x} , v _{f y} ) = ____________m/s

maximum displacement   ( Δd _x , Δd _y ) = __________m

 

Press the green button beside the once to see the final velocity in terms of x and y components.

final velocity              ( v _{f x} , v _{f y} ) = ____________m/s

 

Note that the acceleration due to gravity is ignored in this simulation.

 

Analysis

 

Self-Check Answer the following self-check (SC) questions then click the "Check your work" bar to assess your response.

 

Note that the values will be close to, but not necessarily exactly the same as, the answers shown. This is because you might have a slightly different time, ±0.20 s. However, your results will match the simulation's values.

 

SC 7.  

Use Newton's laws of motion to verify the x and y components of the acceleration.

 

SC 8.  

Use calculations to verify the x and y components of the maximum displacement.

 

SC 9.  

Describe and explain a situation involving gravitational fields that could produce a similar type of motion.