Experiment 1: Review of Vector Addition

Part A:Review Vector Addition

We will/ or have gone over the general process of taking two or more vectors, breaking each into components, adding the total x and y components, and then constructing a resultant. Review these concepts.

Part B:Physlet Simulation

Briefly examine Physlet Illustration 3.1—Chapter 3 in physlets (Link to this from Physlets.) Next examine Physlet PROBLEM 3.2. Your goal is to go through the vector addition process described in part A.

x / y
Red
Blue
Resultant

Resultant magnitude=______

Resultant angle=______

Part C: An example of vector addition

The electric force between two charged objects depends on the separation of the objects r, and the amount of charge on each object (given by q1or q2). The magnitude of the electric force is given by “Coulomb’s Law

k=9.0x109N m2/(C2)

Procedure:

  1. Blow up two balloons so that they are roughly the same size.
  2. Weigh several balloons on a scale and determine the average mass of a single balloon.
  3. Carefully determine a length of thread so that the two balloons hang just above the floor. Use some tape at the pivot so that each thread has the same length.
  4. Charge up both balloons by rubbing on your hair, or rubbing with the provided fur. Touch the balloons together so that they will have the same charge on each.
  5. The charged balloons will now separate due the repulsive electrical force..
  6. Quickly measure the distance “r” between the balloons.
  7. Measure the height from the center of the hanging balloons to where the string is tied.

Analysis:

  1. Sketch a free-body force vector diagram for balloon 1.
  2. Determine the angle  from the geometry.
  3. For the three forces acting on balloon 1 make a table indicating horizontal and vertical components for each of the three vectors and also the sum for each (horizontal and vertical).
  4. Now use your measurements to determine the magnitude of tension, and electric force acting on balloon 1.
  5. Now that you have the magnitude of electric force, determine the magnitude of charge on each balloon. You will need to use the Coulomb constant “k” above and note that SI units for charge are in Coulomb’s (denoted by “C”).

Questions: Use Coulomb’s law to answer the following.

  1. What will happen to the electric force if the charge on each balloon is doubled but the distance is kept the same?
  2. What will happen if the distance is doubled, but with your original charge?