A. 0.5kg
To get this answer you need to follow the equation of KE=0.5*mv^2
But we don't have the m part in the equation. So just plug in the numbers to see which works best, though I can tell you before we do that the answer would be a.
As you may know, gravity, is a force of 9.8 m/s. And we want to get 9.8 Joules. So if we take a half a kg stone, release it at one meter, we get half of the normal gravity pull, 4.90 Joules. That means if we take half a kg stone and drop it at a doubled height, we get 9.8 Joules.
That is also to say that if we have a 1kg stone and drop it at one meter you will get the normal pull of gravity in Joules, 9.8J.
Be careful though, this does not mean if you drop a 1kg stone and a .5 kg stone the 1kg will hit first. This simply means that the 1kg stone will have twice the Joules that the .5kg stone has.
The diameter of the sphere is 2cm.
<h3>How to calculate the diameter?</h3>
From the diagram, the first sphere on the ruler is at 4cn and the last sphere is at 12cm.
Therefore, the length will be:
= 12 - 4.
= 8cm
The diameter of one sphere will be:
= Length / 4
= 8/4
= 2
Therefore, the diameter of the sphere is 2cm.
Note that the second question wasn't found online.
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When light travels from a medium with higher refractive index into a medium with lower refractive index, there is a maximum angle (called critical angle) for which all the light is reflected, so there is no refraction.
The value of the critical angle is given by:

when n1 is the refractive index of the first medium, while n2 is the refractive index of the second medium. In our case, n1=1.33 (the water) and n1=1.00 (the air). Putting numbers in, we get
A particle with charge -40.0nC is on the x axis at the point with coordinate x=0 . A second particle, with charge -20.0 nC, is on the x axis at x=0.500 m.
No, there is no point at a finite distance where the electric potential is zero.
Hence, Option D) is correct.
What is electric potential?
Electric potential is the capacity for doing work. In the electrical case, a charge will exert a force on some other charge and the potential energy arises. For example, if a positive charge Q is fixed at some point in space, any other positive charge when brought close to it will experience a repulsive force and will therefore have potential energy.
It is also defined as the amount of work required to move a unit charge from a reference point to a specific point against an electric field.
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Answer: The correct answer for the blank is -
C. closure.
Gestalt principle of closure describes how we perceive complete figures even when the information that form the figure is missing.
This is due the fact that our brain responds to the familiar patterns inspite of getting incomplete information.
For instance, in the given question, we are able to perceive an image of square in the center despite not having actual lines that form a square.
Thus, it represents principle of closure.