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.
Linear expansion means change in one dimension (length) as opposed to change in volume (volumetric expansion). To a first approximation, the change in length measurements of an object due to thermal expansion is related to temperature change by a linear expansion coefficient. It is the fractional change in length per degree of temperature change.