You find yourself in a place that is unimaginably <u>hot and dense</u>. A r<u>apidly changing</u><u> gravitational field</u><u> </u>randomly warps space and time. Gripped by these huge fluctuations, you notice that there is but a single, unified force governing the universe, you are in the early universe before the Planck time.
<h3>What is Planck time?</h3>
The Planck time is approximately<u> 10^-44 seconds</u>. The smallest time interval, or "zeptosecond," that has so far been measured is <u>10^-21 seconds</u>. A photon traveling at the speed of light would need one Planck time <u>to traverse a distance of one </u><u>Planck length</u>.
<h3>What is Planck length?</h3>
Planck units are a set of measuring units used only in particle physics and physical cosmology. They are defined in terms of <u>four universal </u><u>physical constants</u> in such a way that when expressed in terms of these units, these physical constants have the numerical value 1. These units are a system of natural units because its definition is <u>based on characteristics of nature</u>, more especially the characteristics of free space, rather than a selection of prototype object, as was the case with Max Planck's original 1899 proposal. They are pertinent to the study of unifying theories like quantum gravity.
To learn more about Plank time:
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As per Bernuolli's Theorem total energy per unit mass is given as

now from above equation




now by above equation


Part B)
Now energy per unit weight



Answer:
The velocity of the truck after this elastic collision is 15.7 m/s
Explanation:
It is given that,
Mass of the car, 
Mass of the truck, 
Initial velocity of the car,
Initial velocity of the truck, u₂ = 0
After the collision the velocity of the car is, v₁ = -11 m/s
Let v₂ is the velocity of the truck after this elastic collision. Using the conservation of momentum as :

So, the velocity of the truck after this elastic collision is 15.7 m/s. Hence, the correct option is (c).
C 1.6 amps hipe this helps