Rocket observations show that dust particles in Earth’s upper atmosphere are often electrically charged. (a) Find the distance separating two dust particles if each has a charge of +e and the Coulomb force between them has magnitude 1.00 × 10 −14 N. (b) Calculate the mass of one of the dust panicles if this Coulomb force would accelerate it at 4.50 × 10 8 m/s 2 . (In the upper atmosphere, effects from other nearby charges typically result in a small net force and acceleration.)

In 1911, Ernest Rutherford and his assistants Geiger and Marsden conducted an experiment in which they scattered alpha particles (nuclei of helium atoms) from thin sheets of gold. An alpha particle, having charge +2e and mass 6.64 x 10-27 kg, is a product of certain radioactive decays. The results of the experiment led Rutherford to the idea that most of an atom's mass is in a very small nucleus, with electrons in orbit around it. Assume an alpha particle, initially very far from a stationary gold nucleus, is fired with a velocity of 2.98 × 107 m/s directly toward the nucleus (charge +79e). What is the smallest distance between the alpha particle and the nucleus before the alpha particle reverses direction? Assume the gold nucleus remains stationary. fm

Two identical positive charges exert a repulsive force of 6.6 × 10−9 N when separated by a distance 3.9 × 10−10 m. Calculate the charge of each. The Coulomb constant is 8.98755 × 109 N · m2 /C2 . Answer in units of C. Answer in units of C.

Red blood cells can often be charged. Consider two red blood cells with the following charges: -24.6 pC and +51.6 pC. The red blood cells are 3.58 cm apart. a) What is the magnitude of the force on each red blood cell? b) The red blood cells come into contact with each other and then are separated by 3.58 cm. What magnitude of force does each of the red blood cells now experience?