18. 19. 20. When two small charged spheres are separated by 2.0 m, the electrical force of attraction between them is 8.0 N. If the charge on each sphere is doubled and the separation is reduced to 1.0 m, the force of attraction will now be (a) s N (b) 16 N (c) 24 N (d) 48 N (e) 96 N Two spheres, X and Y, are 4 m apart. A charge of 2 Q is distributed over sphere X and a charge of Q is distributed over sphere Y. The magnitude of the electrostatic force on X is (a) 4 times that on Y (b) 2 times that on Y (c) the same as that on Y {d} onehalf that on Y (e) one quarter that on Y The neutral particles contained in the nucleus of an atom are called (3) alpha particles {b} electrons (c) ions (d) neutrons (e) protons 21. A certain force gives mass m, an acceleration of 12 m/s2. The same force gives mass m2 an acceleration of 3.0 m/s2 What acceleration would the force give to an object whose mass is the difference between m, and m2? (a) 2.4 m/s2 (b) 4.0 m/s2 (c) 6.0 m/s2 (d) 9.0 m/s2 (e) The acceleration cannot be determined from the information given. 22. Which of the following diagrams most correctly describes the electric field in the vicinity of two small isolated oppositely charged spheres? (A ) (B) (C) (D) ( E ) K