Coulomb Force (Static) Gizmo Answer Key

Name: Yahir Booker Date: 08-10-2022 Student Exploration: Coulomb Force (Static) 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, vector Prior Knowledge Questions (Do these BEFORE using the Gizmo.). Have you ever taken clothes out of the dryer and found a sock stuck to your underwear? Static cling is an example of electrostatic forces, or the forces that exist between charged objects. 1. How do you think the sock and underwear became charged? Electrons were transferred from certain clothing articles to others throughout the drying process. 2. Suppose two socks acquire the same charge. Do you think they would stick together? Explain: Because like charges repel, the socks would not cling together. Gizmo Warm-up As clothes are tumbled in a dryer, electrons are rubbed off some items, giving them a positive charge, and deposited on other items, giving them a negative charge. These charged items exert electrostatic forces on one another. You can explore these forces with the Coulomb Force (Static) Gizmo. In its initial settings, the Gizmo shows two objects that each have a charge (q) of 10.0 × 10-4 C (coulombs). Turn on the Show force vector checkboxes for objects A and B. The arrows coming from each object are vectors that represent the electrostatic force. The direction and length of each vector show the direction and magnitude (strength) of each force. 1. Are the vectors for objects A and B pointing together or away from each other? Away 2. Are objects A and B attracted together or repelled apart? Repelled apart 3. Compare the lengths of the vectors. What do you notice? The length of the vectors is the same. Activity A: The effect of charge Get the Gizmo ready: ● Turn on Show grid. Place object A on the x-axis at -5 and object B on the x-axis at +5. ● Check that Show force vector is turned on for each object. Question: How does charge affect the strength of the electrostatic force? 1. Observe: You can change the charge of each object by entering the desired value in the qA and qB boxes. Observe the force vectors for each of the situations listed in the table below. Based on the force vectors, state whether the objects are repelled from one another, attracted to one another, or if there is no force at all. qA 1.0 × 10-4 C -1.0 × 10-4 C -1.0 × 10-4 C 1.0 × 10-4 C qB 1.0 × 10-4 C 1.0 × 10-4 C -1.0 × 10-4 C 0.0 × 10-4 C Attraction, repulsion, or no force? Repulsion Attraction Repulsion No force 2. Make a rule: Complete the following sentences with the words “attract,” “repel,” or “zero.” When the charges are the same, the two objects repel one another. When the charges are opposite, the two objects one another. attract When one of the objects has no charge, the resulting force is zero. 3. Predict: How do you think the magnitude of the electrostatic force between two objects will change if the charge of each object was doubled? The forecasts will differ. 4. Measure: Turn on Show vector notation for both objects. Set the charge of objects A and B to 1.0 × 10-4 C. The force on object A is now -0.90i + 0j N. That means that the force is -0.90 N in the x direction and 0 N in the y direction. A. What is the magnitude of the force on object A? |FA| = 0.9 N B. What is the magnitude of the force on object B? |FB| = 0.9 N C. The force on object A is negative. What does this indicate about the direction of the force? The negative value denotes that the force acting on A is left-pointing. 5. Gather data: For each charge combination listed in the table below, write magnitude of the force on object A. (Note: The magnitude of the force, or its strength, is always positive.) qA qB -4 -4 |FA| Factor 1.0 × 10 C 1.0 × 10 C 0.9 N 1 1.0 × 10-4 C 2.0 × 10-4 C 1.8 N 2 2.0 × 10-4 C 2.0 × 10-4 C 3.6 N 4 2.0 × 10-4 C 3.0 × 10-4 C 5.4 N 6 qA × qB 6. Analyze: What patterns do you notice in the data? The force doubles when one charge is multiplied by two. The force increases by a factor of four when both charges are increased. 7. Calculate: To calculate how much the force is multiplied, divide each force by the first value, 0.90 N. Fill in these values under Factor in the table. What do you notice? The factor doubles when one of the forces is doubled. 8. Calculate: Calculate the product of the two charges, and fill in these values in the last column. Compare these numbers to the Factor numbers. What do you notice? The product is proportional to the force factor. 9. Apply: What would you expect the force to be if the charge of object A was 5.0 × 10-4 C and the charge of object B was 4.0 × 10-4 C? Check your answer with the Gizmo. 18.0 N 10. Challenge: Based on what you have learned, write an equation for the strength of the electrostatic force for two charges that are separated by 10 meters. Use the Gizmo to check your equation. F= Activity B: Get the Gizmo ready: ● Turn on Show distance. ● Set qA to 10.0 × 10-4 C and qB to 1.0 × 10-4 C. The effect of distance Question: How does distance affect the strength of the electrostatic force? 1. Observe: Move object A back and forth. How does the distance between the objects affect the strength of the electrostatic force between them? The electrostatic force weakens and the items separate as a result. 2. Predict: How do you think the electrostatic force between two objects would change if the distance between the two objects was doubled? The forecasts will differ. 3. Measure: Place object A on the x-axis at -2, and object B on the x-axis at +1. A. What is the magnitude of the force on object A? |FA| = 100 N B. What is the magnitude of the force on object B? |FB| = 100 N 4. Gather data: Check that qA is 10.0 × 10-4 C and qB is 1.0 × 10-4 C. For each position of object A, record the distance between the objects and the force on object A. Object A (-2, 0) (-5, 0) (-11, 0) (-14, 0) Objec tB (1, 0) (1, 0) (1, 0) (1, 0) Distance (m) 3m 6m 12 m 15 m |FA| (N) 100 N 25 N 6.25 N 4N Distance factor 1 2 4 5 Force factor 1.00 0.250 0.0625 0.04 1 Dist. factor2 1.00 0.250 0.0625 0.04 5. Calculate: To calculate the distance factor, divide each distance by the original distance (3 m). To calculate the force factor, divide each force by the original force (100 N). A. How does the force change as the distance increases? As the distance widens, the force weakens. B. Now find the reciprocal of each distance factor squared. The reciprocal of the What do you notice? square of the distance factor is the force factor. 6. Apply: What would you expect the force to be if the distance was 30 meters? 1N How did you come up with your answer? The distance factor is 10 (30 m ÷ 3 m). The reciprocal of the distance factoris 0.1. The square of this value is 0.01. Therefore the force factor is 0.01 and the resulting force is 0.01 × 100, or 1 N Use the Gizmo to check your answer. 7. Make a rule: Based on what you have learned, write an equation to calculate the force between two objects if the product of their charges is 1.0 × 10-7 C. Use the Gizmo to test your formula. (Note: Use the variable R for the distance between the charges.) F= 8. Summarize: Fill in the blanks. The electrostatic force between two objects is proportional to the reciprocal of the distance squared 9. Challenge: Coulomb’s law is an equation that relates the electrostatic force between two objects to their distance and charge. In activity A, you found that the electrostatic force between two objects is proportional to the product of their charges. Combine that with what you have learned in this activity to complete Coulomb’s law below. (Hint: In the equation, k is a constant.) Check your answer with your teacher. Click the image to select EDIT to use the text box. 10. On your own: Use the Gizmo to find the value of k in the formula above. List the value and describe how you found it below. The units of k are newton · meter2 ÷ coulombs2, or N·m2/C2. Check your answer with your teacher. k= Show your work: