The speed of the rock at 20 m is 34.3 m/s
Explanation:
We can solve this problem by using the law of conservation of energy: the mechanical energy of the rock, sum of its potential energy + its kinetic energy) must be conserved in absence of air resistance. So we can write:
where
:
is the initial potential energy
is the initial kinetic energy
is the final potential energy
is the final kinetic energy
The equation can also be rewritten as follows:
where:
m = 100 kg is the mass of the rock
is the acceleration of gravity
is the initial height
u = 0 is the initial speed (the rock starts at rest)
is the final height of the rock
v is the final speed when h = 20 m
And solving for v, we find:
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The answer is D. Small object made of ice and dust that orbits the Sun and forms a coma as it approaches the Sun.
Answer:
1) ironing a shirt 2) writing on surfaces 3) working of an eraser
Bio-gas is the naturally produced fossil fuel, a by-product when bacteria decompose organic material under anaerobic conditions.
<h3><u>Explanation:</u></h3>
Organic matter particularly waste material is broken down by bacteria through fermentation in an environmental condition without any presence of oxygen. This process of decomposition leads to formation of bio-gas with "carbon dioxide and methane" in a 2:3 ratio.
The above biological process is termed as bio-digestion or anaerobic digestion. Methane is flammable and thus bio-gas can be used as "energy source", a waste-to-energy transformation. The remaining decomposed matter is ideal as manure for plants due to its rich nutrient level.
5g/cm³
it is not iron.
Explanation:
Given parameters:
Density of iron = 7.874g/cm³
Mass of metal = 2000g
Volume of metal = 400cm³
Unknown:
Density of bar = ?
Is it iron = ?
Solution:
The density of a substance is its mass per unit area. Every substance have an intensive density value that typifies them all.
The density of water and other substances are the same if they maintain their level of pureness.
Density = 
Density of metal bar = 
= 5g/cm³
Since this value is not the same as the given density of iron, it is not iron.
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