Page 7 - Simplied Force

SIMPLIFIED COURSE ON SEE SCIENCE : CHAPTER- FORCE

Some Give Reason Questions:

• Force is a vector quantity.

To fully describe the force acting upon a body, we must specify both the magnitude and direction. So, force
is a vector quantity.

• The effects of gravitational pull of the sun and moon is more in liquids on the earth.

In solids molecules are tightly packed with strong force of attraction. But the force of attraction is weaker
in the molecules of liquids. So, liquid molecules move easily. The same gravitational pull on solids and
liquids may cause the liquid to flow instead of change in shape of the solids. So. the effect of gravitational
pull of the sun and moon is more in liquids on the earth.

• We do not see a falling apple attracting the earth towards itself.

The gravitational force between the earth and the apple is very weak due to less mass of the apple. Due to
less mass of the apple it cannot produce noticeable acceleration in the earth but the earth having more mass
produces noticeable acceleration in the apple. Thus, we do not see a falling apple attracting the earth towards
itself.
• Newton’s law of gravitation is called universal law.

Newton’s law of gravitation is valid for the force of attraction between any two bodies in the universe. Such
two bodies are from tiny microscopic objects (the atoms) to huge celestial object like stars, planets, galaxies,
etc. So. Newton’s law of gravitation is called universal law.

• The gravitational constant is called a universal constant.

The value of gravitational constant doesn't depend on the nature of the medium between two bodies. It also
doesn't depend on masses of the bodies. The value of G is same for all pairs of objects, at all distances of
separation. So, the gravitational constant is called a universal constant.

• There is a mutual force of attraction between two students sitting on a bench but they do not move
toward each other.

According to Newton’s universal law of gravitation, there is a mutual force of attraction between two
students sitting on a bench but they do not move toward each other. This is because the gravitational force
between two small masses is weak in nature. Such weak force is not experienced at all.

• Acceleration due to gravity of the earth is 9.8m/s2. What does it mean?

Acceleration due to gravity of the earth is 9.8m/s which means, when an object is falling freely under the
influence of the earth’s gravity, its velocity increases at the rate of 9.8m/s.

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