7. A balloon weighs 9.8 x 10-*N. If two uniformly charged balloons are brought together, one with Q and the other with -Q, what should Q be so that the attraction between them = mg?

Two balloons are charged with an identical quantity and type of charge: -7.25 nC. They are held apart at a separation distance of 59.7 cm. Determine the magnitude of the electrical force of repulsion between them.

4. Consider three infinite line charges with charged densities A, -2 A, 3 A placed at y = d, 0, -d respectively. What is the net electric field at the point y = d/2? Set the upwards direction as the positive direction. (See diagram) y = d y = d/2 y = 0 -2A y = -d 3A A. E = 0 E В. 2 περά -2) E С. TEnd E = D. TEnd B.

1. Two point charges exert a 9.50 N force on each other. What will the force (in N) become if the distance between them is increased by a factor of 3? 2. Red blood cells often can be charged. Two red blood cells are separated by 1.30 m and have an attractive electrostatic force of 0.971 N between them. If one of the red blood cells has a charge of +8.64  10-6 C, what is the sign and magnitude of the second charge, Q?

32. Humid air breaks down (its molecules become ionized) in an electric field of 3.0 × 10° N/C. In that field, what is the magnitude of the electrostatic force on (a) an electron and (b) an ion with a single electron missing?

1. In the following problems, you don't need to understand the physics to complete the questions. Focus on the equations. (a) The force of gravity, F, between two masses, m and M, separated by a distance r, is given by GmM where G is a constant. Write an equation of r in terms of other variables in the equation F= for F: r= GmM F (b) The electric force between two charges q=3-10-6 units and Q=-4·10¯6 units separated by a distance, d = 3.10-4 units, is given by F= kqQ d² I where k=9. 10⁹ units. Without using a calculator, calculate the F. F= -12x10 -5 Ⓡ√

an electrostatic force of 4.2 x 10 N. How far apart are the centers of the two charges? 5. How many electrons st be removed from a neutral, isolated conducting sphere to give it a positive charge of 8.0 x 10 C? ANSWERS 1. a) 1.2 x 10 'N b) 1.5 x 10 N c) 3.3 x 10 0'N 2.1.8 x 10 N 3.1.9x 10 20N 4.5.09 x 1019 m 5. Alicia got 5 x 10 27 electrons DELL

104. In copper there is approximately one free electron for each atom. A copper coin has a mass of m=3 g. (k=9.10° N.m²/C², NA=6.02.10²3 mol-¹, e--1.6.10-¹9 C, M-63.5 g/mol) 1) What percentage of the free charge would have to be extracted from the currency for it to acquire a charge of q=15 UC? a)2,69.107 % b)2,99.107 % c)3,29.10.7 % d)3,59.10-7% e)3,89.107 % II) What would be the force of repulsion between two coins that have this charge, if they were separated by a distance of d = 25 cm? (Assume currency as a point charge) (a)30.4 N b)32.4 N (c)34.4 N (d)36.4 N (e)38.4 N

1. Three identical metallic conducting spheres carry the following charges: 91 = +5.00 μC, q2 = +1.40 µC, and 93 -9.20 μC. The spheres that carry the charges 9₁ and 92 are brought into contact. Then they are separated. After that, one of those two spheres is brought into contact with the third sphere that carries the charge 93; those two are then separated as well. ROJS a) What is the final charge on the third sphere?60 SS μC sf60 s60 s ssf60 ssfo ssf603 60 ssf60 ssi

7. Three positive charges, q1, q2, and q3 are connected with two strings of equal length L. Due to mutual Coulomb repulsion the charges spread out and form a straight line such that the distance between 1 and 3 is 2L and, with 2 in the middle, the distance between 1 and 2 or 2 and 3 is just L. Find the tension force in each string.