4. a spherical shell with outer radius b surrounds a charge-free cavity of radius a < b. if the shell contains a charge density given by   0 3 2 c/m for 0 elsewhere v v arb r r           a. find the electric field e in all regions b. determine the electric potential v in all regions c. determine the electrostatic energy stored for r  a, a  r  b, and r  b.

What are the necessary conditions for fusion?

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.