Q. A block of a solid is known to contain many dipoles aligned in the same direction (such a material is known as an electret). In an electric field of magnitude 120 N/C, the block tends to orient itself so that the dipoles are aligned along the electric field lines. If 7.6 J are required to rotate the solid so that the dipole directions are reversed, and each dipole has dipole moment 8.6 × 10-30 C-m, how many dipoles are there in the block?

Q. Many people mistakenly believe that the astronauts who orbit earth are above gravity. earth's mass is 6x10square root 24 kg, and its radius is 6.38x10 square root 6 m (6380 k). use the inverse square law to show that in space shuttle territory, 200 kilometers above earth's surface, the force of gravity on a shuttle is about 94% of that at earth's surface.