Price for first-class stamp rises to 49 cents. It's going to cost you a few pennies more to mail a letter. The cost of a first-class postage stamp is now 49 cents â 3 cents more than before. 1  Regulators approved the price hike in December, and it went into effect Sunday. 2  Many people won't feel the increase right away: Forever stamps are good for first-class postage at whatever the future rate.
Expansion joint in a road bridge used to avoid damage from thermal expansion. Thermal expansion is the tendency of matter to change in shape, area, and/or volume in response to a change in temperature, through heat transfer. Temperature is a monotonic function of the average molecular kinetic energy of a substance. When a substance is heated, the kinetic energy of its molecules increases.
This is called an. expansion. In an isothermal process the internal energy remains constant and we can write the First Law as 0 = q + w, or q = w, illustrating that the heat flow and work done exactly balance each other. Because no thermal insulation is perfect, truly adiabatic processes do not occur.