Using Coulombs Law

9. Two small spheres, with charges 1.6 x 10-C and 6.4 x 10 5C. are 2.0 m apart. The charges have the same sign. Where, relative to these two spheres, should a third sphere, of opposite charge 3.0 x 10-6 C. be placed if the third sphere is to experience no net electrical force? Do we really need to know the charge or sign of the third object? 10. Two spheres are attached to two identical springs and separated by 8.0 cm, as in Figure 14. When a charge of 2.5 x 10 C is placed on each sphere, the distance between the spheres doubles. Calculate the force constant k of the springs. 8.0 cm Figure 145. Two identically charged small spheres, of negligible mass, are separated by a centre-to-centre distance of 2.0 m. The force between them is 36 N. Calculate the charge on each sphere. 6. Neutral metal sphere A. of mass 0.10 kg. hangs from an insulating wire 2.0 m long. An identical metal sphere B. with charge -q, is brought into contact with sphere A. The spheres repel and settle as shown in Figure 11. Calculate the initial charge on B. 120 :.. B A Figure 11 7. Three objects with charges +5.0 AC, -6.0 /C, and +7.0 AC are placed in a line, as in Figure 12. Determine the magnitude and direction of the net electric force on each charge. +5.0 AC -6.0 AC +7.0 AC --- 0.80 m 0.40 m Figure 128. Three objects, carrying charges of -4.0 x 10- C, -6.0 x 10-6 C, and +9.0 x 10 6C. are placed in a line, equally spaced from left to right by a dis- tance of 0.50 m. Calculate the magnitude and direction of the net force acting on each. 9. Three spheres, each with a negative charge of 4.0 x 10 * C, are fixed at the ver- tices of an equilateral triangle whose sides are 0.20 m long. Calculate the mag- nitude and direction of the net electric force on each sphere.2. Two identical metal spheres, each with positive charge q, are separated by a centre-to-centre distance r. What effect will each of the following changes have on the magnitude of the electric force F exerted on each sphere by the other? (a) The distance between the two spheres is tripled. (b) The distance between the two spheres is halved. (c) Both charges are doubled. (d) One of the charges becomes negative. (e) One sphere is touched by an identical neutral sphere. which is then taken far away and the distance is decreased to 3. Two small spheres of charge +5.0 /C and -4.0 AC are separated by a distance of 2.0 m. Determine the magnitude of the force that each sphere exerts on the other. 4. Two 10.0-kg masses, each with a charge of + 1.0 C, are sep- arated by a distance of 0.500 km in interstellar space, far from other masses and charges. (a) Calculate the force of gravity between the two objects. (b) Calculate the electric force between the two objects. (c) Draw FBDs showing all the forces acting on the objects. (d) Calculate the net force on each object, and use it to find the initial acceleration of each object. (e) Repeat (c) ignoring the gravitational force. What have you found