Explanation

The gravitational force between two objects is independent of the medium between them.

Gravity acts through a vacuum just as it does through a medium like air, water, or solid objects.

The presence or absence of a medium does not affect the gravitational force between the objects.

Explanation

The weight of a body is the force exerted on it by gravity.

It depends on the gravitational pull of the planet or moon it is on.

Since the gravitational pull varies from place to place (it is stronger near the surface of the Earth than on a mountain, and weaker on the Moon than on the Earth), the weight of a body also varies.

Explanation

The Earth's Moon has considerably less mass than the Earth itself.

Not only is the Moon smaller than the Earth, but it is only about 60 percent as dense as Earth.

Thus, the gravitational attraction on the Moon is much less than it is here on Earth, and a person weighs less on the Moon.

ND20-1-2023

Explanation

The force of friction opposes the motion of an object, causing moving objects to lose energy and slow down.

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ND18-1-2023

Explanation

Brewster’s angle is the angle of incidence at which light with a particular polarization is perfectly transmitted through a surface with no reflection.

At this angle, the reflected and refracted rays are perpendicular (90° apart).

Explanation

The speed of sound in a gas is proportional to the square root of temperature (in Kelvin):

v ∝ √T

If the temperature becomes 16 times, then:

New speed = √16 × original speed = 4 × original speed

Explanation

 A LASER beam can be sharply focused because it is highly coherent. 

Coherence refers to the well-organized nature of light waves in a laser beam, where all the waves are in phase with each other, allowing them to be concentrated into a small, focused spot

Explanation

The statement "The mechanical energy spent by the external agency is converted into electrical energy stored in the coil" relates to Lenz's law. 

Explanation

Explanation

The substance reduces to (1/16) = (1/2)^4 of its original mass.  

This means 4 half-lives = 40 days  

So, 1 half-life = 40 / 4 = 10 days