Page 15 - Simplied Force

SIMPLIFIED COURSE ON SEE SCIENCE : CHAPTER- FORCE

19 A person does not get injured when he/she falls with a parachute on the earth from the
airplane.

Due to large surface area of the parachute, the air resistance will be more. As a result, the acceleration
of the parachute decreases. The decreased acceleration due to gravity causes the person to fall down
slowly. Consequently, the person can land safely without getting injured.
20 Write any two effects of gravitation.

The two effects of gravitation are:
1. Presence of atmosphere around the earth
2. Stability of planets around the sun in the solar system

21 Why does a body fall faster in the polar region of the earth than in the equatorial region?

In the equatorial region, the radius of the earth is more. Acceleration due to gravity is less in this
region as it is inversely proportional to the square of the radius of the earth. Due to less acceleration,
the object falls slower. While in the polar region, the radius of the earth is less and the acceleration
due to gravity is more. So, the object falls faster in the polar region due to more acceleration due to
gravity.

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22 The value of gravitational constant is 6.67 x 10 Nm /kg . What does it mean?
It means the gravitational force of attraction between two unit masses which are separated by unit
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distance is 6.67 x 10 N.
23 State Newton’s universal law of gravitation.
Newton’s universal law of gravitation states that everybody in this universe attracts every other body
with a force which is directly proportional to the product of their masses and inversely proportional to
the square of distance between their centres.

24 A person in an artificial satellite of the earth feels weightless. But the same person on the moon
has some weight though the moon is also a satellite of the earth. Why?

In the artificial satellite, there is no gravitation but on the surface of the moon, gravity is present with
its effect in very little amount. Thus, a person feels weightlessness due to the absence of gravity on
the artificial satellite but has some weight on the surface of the moon.

25 The moon has no atmosphere. Give reason.

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The value of the gravity on the surface of moon is 1.652m/s . Therefore, the value of escape velocity
on the surface of moon is small. The velocity of the molecules of different gases is much above the
escape velocity of the moon. That is why, all the molecules of gases escaped and there is no atmosphere
on the moon.

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