1. Two identical metal balls are suspended by insulating threads. Both balls have the same net charge. In this problem, do not assume the balls are point charges Ball 2 a. Draw a separate free-body diagram for each ball. Label the forces to indicate: . the object exerting the force, the object on which the force is exerted, • the type of force (gravitational, normal etc.), and • whether the force is a contact or a non- contact force. Preo-body diagram for ball : Free-body diagram for all 2 b. Suppose the charge on the second ball is reduced slightly, so that it is less than that on the first ball. Predict whether the angle that ball 1 minkes with the vertical will be greater than, less than or equal to the angle that ball 2 makes – with the vertical. Explain. Sketch your answer above. How does the free body dingram for each ball in this case compare to the corresponding free body diagram that you drew in part a? If the magnitudes or directions of any of the forces change, describe how they change C. Predict what will happen if the nel charge on ball 2 is reduced to ro. Make a sketch to illustrate your answer

M Charge 2. Coulomb’s law allows us to find the force between two point charges. Three point charges are held fixed in place as shown. SH Consider the following comment about this situation: “There will be zero het electric force on the change in the middle due to the other changaa Using Coulomb’s law, the force due to the charas is posities and the force due to the charge le noastre. The forces canical a. Do you agree with this statement? Explain. b. How does Coulomb’s law apply to situations in which there are more than two point charges 3. Each of the following parts involves a comparison of the net electric force exerted on a positive charge + in two different cases. a. In cases A and B shown at right there are two positive point charges + each a distances away from a third positive point charge to. + Is the net electric force on the + charge in case A greater than, less than or equal te the net electric force on the + charge in case B? Explain b. In case C, two positive point charges +20 are each a distances away from a third positive point charge +o. In case D, four positive point charges are cacha distance away from a fifth positive point charge . The angle a shown is the same in both cases.) Is the net electric force on the + charge in case C grewer whan, less than or equal to the net electric force on the + charge in case D? Explain. Gustice Hall Twiatru introductory Physics McDermo, Shafer, PG, U. Wah.

CHARGE c. In case B a positive point charge with +0 is a distances away from a third positive point charge . In case F ten positive point charges, each with charge +O/10, lie along an are of radiuss centered on a positive point charge . Case Is the set electric force on the to charge in case Egreater than, less than or equal to the net electric force on the charge in case F? Explain. 4. Athin semicircular rod has a total charge + uniformly distributed along it. A negative point change is placed as shown. A test charpe + is placed at point C. (Point C is equidistant from and from all points on the rod.) Let P, and represent the force on the test charge due to the point charge and the rod respectively. Is the magnitude of greater than, less than or equal to the magnitude of F,? Explain how you can tell force on + fewer than less than or equal to the magnitude of Is the magnitade of the F, Explain. c. A second negative point charges – is placed as shown. Is the magnitude of the electric force on erwater thon, less than or equal to the magnitude of the net electric force on +g in part b? Explain. ir 2000 Zistorise MD demory Phy , Shafer, PE, tt. Wish

EM Charge 78 5. A thin semicircular rod like the one in problem 4 is broken into two halves. The top half has a total charge uniformly distributed along it, and the bottom half has a total charge – uniformly distributed along it. On the diagram, indicate the direction of the net electric force on a positive test charge placed in tum at points A, B, and C. Explain how you determined your answers. 6. A positive point charge +g is placed near an uncharged metal rod. Uncharged metal rod a. Sketch the charge distribution on the rod. b. Is there a non-zero net electric force on the rod? Explain. c. Is there a non-zero not electric force on the point charge? Explain. Case A Neutral 7. State whether the magnitude of the net electric force on the charge labeled + in case A is greater than, less than or equal to the magnitude of the net electric force on the charpe labeled +. in case B. Explain how you determined your answer. + Twarials in Patrasciory Physics Memoll, Shaffer, E.G.U. Wash