The time spent in the air by the ball at the given momentum is 6.43 s.
The given parameters;
- <em>momentum of the ball, P = 0.9 kgm/s</em>
- <em>weight of the ball, W = 0.14 N</em>
The impulse experienced by the ball is calculated as follows;
where;
is impulse
is change in momentum
The time of motion of the ball is calculated as follows;
Thus, the time spent in the air by the ball at the given momentum is 6.43 s.
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<h2>
Answer: 0.17</h2>
Explanation:
The Stefan-Boltzmann law establishes that a black body (an ideal body that absorbs or emits all the radiation that incides on it) "emits thermal radiation with a total hemispheric emissive power proportional to the fourth power of its temperature":
(1)
Where:
is the energy radiated by a blackbody radiator per second, per unit area (in Watts). Knowing 
is the Stefan-Boltzmann's constant.
is the Surface area of the body
is the effective temperature of the body (its surface absolute temperature) in Kelvin.
However, there is no ideal black body (ideal radiator) although the radiation of stars like our Sun is quite close. So, in the case of this body, we will use the Stefan-Boltzmann law for real radiator bodies:
(2)
Where 
is the body's emissivity
(the value we want to find)
Isolating from (2):
(3)
Solving:
(4)
Finally:
(5) This is the body's emissivity
The role of friction is of great importance when creating safety ramps and escalators because with the help of friction things move.
<h3>Why is it important to move objects slowly on ramps and escalator?</h3>
It is important to move objects slowly on ramps and escalator because the ramps and escalator moves object in the opposite direction of gravity. If we did not move objects slowly, then the objects or a person get damaged.
So we can conclude that the role of friction is of great importance when creating safety ramps and escalators because with the help of friction things move.
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<h3><u>Answer;</u></h3>
The different atoms have different quantized energy levels
<h3><u>Explanation;</u></h3>
- The atoms of different elements have different energy levels because they have different nuclear charges and spins, and different numbers of electrons.
- Each different kind of atom, like hydrogen or radon, has a distinct nuclear charge and number of electrons. This makes the potential energy function different for each atom, and therefore results in different energy levels.
- In an emmission spectra, each bright band corresponds to a difference between energy levels within the atom.
