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.
In physics, a form of energy associated with the movement of atoms and molecules in any material. The higher the temperature of a material, the faster the atoms are moving, and hence the greater the amount of energy present as heat.