Pith Ball Lab (answered) Gizmoz; Student Exploration: Pith Ball Lab

Pith Ball Lab Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: Coulomb’s law, electrostatic force, gravitational force, induced charge, pith ball, Pythagorean Theorem, tension, vector Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. A girl rubs a balloon on her head and then holds it a short distance away. Why does her hair stick to the balloon? 2. Why do you think the individual strands of hair are spread apart? Gizmo Warm-up The girl’s hair was attracted to the balloon by the electrostatic force, a force between all charged objects. Most objects acquire a charge (q) by gaining or losing electrons. Objects that gain electrons become negatively charged, while objects that lose electrons become positively charged. The Pith Ball Lab Gizmo shows two pith balls hanging by strings. Pith balls are made from lightweight material that can easily acquire a charge. To begin, check that the charge on each pith ball (q and q ) is 0.0 × 10-6 coulombs (C). Use the sliders to test each combination of charges listed below. State whether the electrostatic force is attractive (balls move together), repulsive (balls move apart), or zero (balls don’t move). Charge on left ball (q1) Charge on right ball (q2) Electrostatic force Positive Zero Zero Negative Positive Positive Negative Negative Positive Negative Activity A: Get the Gizmo ready: ● Set q and q to 0.0 × 10-6 C. Coulomb’s law ● Set the mass of the pith balls to 5 grams. ● Check that g is 9.8 m/s2 and L is 0.50 m. Question: What factors affect the force between charged objects? 1. Summarize: Summarize what you have learned so far by filling in the blanks: If the two charges are the same, the force is If the two charges are opposite, the force is If one of the charges is zero, the force is *Note: For simplicity, the Pith Ball Lab Gizmo does not show induced charge. An induced charge occurs when a charged object is brought near a neutral object, causing the electrons in the neutral object to move away from or towards the charged object. This results in an attractive force between the charged object and the neutral object. 2. Predict: How do you think the strength of electrostatic force is related to the charges on the balls and the distance between them? 3. Observe: Set q to -5.0 × 10-6 C. Gradually decrease q below 0.0 × 10-6 C. A. What do you observe? B. What does this tell you about the force between the pith balls? 4. Observe: Now slowly increase q2 above 0.0 × 10-6 C. What do you observe, and what does this tell you about the electrostatic force? 5. Gather data: Turn on Show angle. For each combination of charges in the table below, record the product of the two charges and the resulting angle. (Note: If you like, you can type the charge values directly into the text boxes to the right of each slider and hit “Enter.”) q1 q2 q1 × q2 Angle 6.0 × 10-6 C 4.0 × 10-6 C 8.0 × 10-6 C 3.0 × 10-6 C 16.0 × 10-6 C 1.0 × 10-6 C -4.0 × 10-6 C -4.0 × 10-6 C 6. Analyze: How does the electrostatic force relate to the product of the charges? Explain. 7. Calculate: Coulomb’s law states that the electrostatic force (Fq) between charged objects is equal to a constant k multiplied by the product of the charges divided by the square of the distance between them: Turn on Show geometric dimensions and Show force vectors and magnitudes. Set q1 and q2 to -5.0 × 10-6 C and the mass to 50 grams. A. What is the distance between the pith balls (R)