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  2. Normal force - Wikipedia

    en.wikipedia.org/wiki/Normal_force

    Figure 2: Weight (W), the frictional force (F r), and the normal force (F n) acting on a block.Weight is the product of mass (m) and the acceleration of gravity (g).In the case of an object resting upon a flat table (unlike on an incline as in Figures 1 and 2), the normal force on the object is equal but in opposite direction to the gravitational force applied on the object (or the weight of ...

  3. Stress (mechanics) - Wikipedia

    en.wikipedia.org/wiki/Stress_(mechanics)

    In continuum mechanics, stress is a physical quantity that describes forces present during deformation. For example, an object being pulled apart, such as a stretched elastic band, is subject to tensile stress and may undergo elongation. An object being pushed together, such as a crumpled sponge, is subject to compressive stress and may undergo ...

  4. Polyphasic sleep - Wikipedia

    en.wikipedia.org/wiki/Polyphasic_sleep

    Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasic (or diphasic, bifurcated, or bimodal) sleep refers to two periods, while polyphasic usually means more than two. [1] Segmented sleep and divided sleep may refer ...

  5. Circadian rhythm - Wikipedia

    en.wikipedia.org/wiki/Circadian_rhythm

    A circadian rhythm (/ sərˈkeɪdiən /), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment). Circadian rhythms are regulated by a circadian clock whose ...

  6. Allostasis - Wikipedia

    en.wikipedia.org/wiki/Allostasis

    Allostasis. Allostasis (/ˌɑːloʊˈsteɪsɪs/) is a physiological mechanism of regulation in which an organism anticipates and adjusts its energy use according to environmental demands. First proposed by Peter Sterling and Joseph Eyer in 1988, the concept of allostasis shifts the focus away from the body maintaining a rigid internal set-point ...

  7. Circular motion - Wikipedia

    en.wikipedia.org/wiki/Circular_motion

    The normal force is actually the sum of the radial and tangential forces. The component of weight force is responsible for the tangential force here (We have neglected frictional force). The radial force (centripetal force) is due to the change in the direction of velocity as discussed earlier. In a non-uniform circular motion, normal force and ...

  8. Contact force - Wikipedia

    en.wikipedia.org/wiki/Contact_force

    The microscopic origin of contact forces is diverse. Normal force is directly a result of Pauli exclusion principle and not a true force per se: Everyday objects do not actually touch each other; rather, contact forces are the result of the interactions of the electrons at or near the surfaces of the objects. [1]

  9. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium ...