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  2. Free-fall time - Wikipedia

    en.wikipedia.org/wiki/Free-fall_time

    The free-fall time is the characteristic time that would take a body to collapse under its own gravitational attraction, if no other forces existed to oppose the collapse.. As such, it plays a fundamental role in setting the timescale for a wide variety of astrophysical processes—from star formation to helioseismology to supernovae—in which gravity plays a dominant ro

  3. Equations for a falling body - Wikipedia

    en.wikipedia.org/wiki/Equations_for_a_falling_body

    Based on wind resistance, for example, the terminal velocity of a skydiver in a belly-to-earth (i.e., face down) free-fall position is about 195 km/h (122 mph or 54 m/s). [3] This velocity is the asymptotic limiting value of the acceleration process, because the effective forces on the body balance each other more and more closely as the ...

  4. Free fall - Wikipedia

    en.wikipedia.org/wiki/Free_fall

    The data is in good agreement with the predicted fall time of /, where h is the height and g is the free-fall acceleration due to gravity. Near the surface of the Earth, an object in free fall in a vacuum will accelerate at approximately 9.8 m/s 2, independent of its mass.

  5. Terminal velocity - Wikipedia

    en.wikipedia.org/wiki/Terminal_velocity

    Based on air resistance, for example, the terminal speed of a skydiver in a belly-to-earth (i.e., face down) free fall position is about 55 m/s (180 ft/s). [3] This speed is the asymptotic limiting value of the speed, and the forces acting on the body balance each other more and more closely as the terminal speed is approached.

  6. Jeans instability - Wikipedia

    en.wikipedia.org/wiki/Jeans_instability

    At the same time, gravity will attempt to contract the system even further, and will do so on a free-fall time = / /, where is the universal gravitational constant, is the gas density within the region, and = / is the gas number density for mean mass per particle (μ = 3.9 × 10 −24 g is appropriate for molecular hydrogen with 20% helium by ...

  7. Geodesics in general relativity - Wikipedia

    en.wikipedia.org/wiki/Geodesics_in_general...

    The first step in such a derivation is to suppose that a free falling particle does not accelerate in the neighborhood of a point-event with respect to a freely falling coordinate system (). Setting T ≡ X 0 {\displaystyle T\equiv X^{0}} , we have the following equation that is locally applicable in free fall: d 2 X μ d T 2 = 0 ...

  8. Projectile motion - Wikipedia

    en.wikipedia.org/wiki/Projectile_motion

    Derivation of the time of flight The total time of the journey in the presence of air resistance (more specifically, when F a i r = − k v {\displaystyle F_{air}=-kv} ) can be calculated by the same strategy as above, namely, we solve the equation y ( t ) = 0 {\displaystyle y(t)=0} .

  9. Time derivative - Wikipedia

    en.wikipedia.org/wiki/Time_derivative

    force is the time derivative of momentum; power is the time derivative of energy; electric current is the time derivative of electric charge; and so on. A common occurrence in physics is the time derivative of a vector, such as velocity or displacement. In dealing with such a derivative, both magnitude and orientation may depend upon time.