Page 9 - Simplied Force

SIMPLIFIED COURSE ON SEE SCIENCE : CHAPTER- FORCE

• A satellite does not need any energy to revolve around the earth.

Satellite does not need any energy to revolve around the earth because of the balanced centripetal and
centrifugal forces provided by the gravitational force.

• The parachutists do not get hurt when they jump out of an aeroplane.

When parachutists jump out of an aeroplane, they accelerate under the effect of gravity. As they open
parachute, the air resistance slows down the speed. Once the force of air resistance balances the force of
gravity, the parachutists no longer accelerate, and come down slowly. So, they do not get hurt.

Some Conceptual Questions with Answers

1) In which direction does the force of gravity act?

Ans: The direction of force of gravity is always acting towards the center of heavenly body.
2) Define null point.

Ans: The space between the gravitational fields of two heavenly bodies, at which the resultant gravity is
zero, is called null point.

3) A satellite does not need any energy to revolve around the earth, why?

Ans: While a satellite is revolving around the earth, the centripetal force due to gravity of the earth is
equal to the centrifugal force due the motion of the satellite. So, a satellite does not need any energy to
revolve around the earth.
4) In which condition do feather and coin dropped from the same height fall at the same speed?
What is the acceleration of the feather and the coin at that instant? Justify your answer.

Ans: A feather and a coin dropped from the same height falls at the same speed at the condition of free
2
fall. At that condition of free fall, both coin and feather gain same acceleration of 9.8m/s . Because the
acceleration produced in the freely falling bodies, whatever their masses, are same in the absence of air
resistance.

5) Write one effect seen on the ocean or sea due to the gravitation of the moon and the sun.

Ans: Tides in sea and ocean are due to the gravitation of the moon and the sun.
6) Where does the weight of the body become maximum in Nepal?

Ans: The weight of the body become maximum at the Terai region of Nepal because the weight of the
body depends upon the acceleration due to gravity (g) and the value of'g' is inversely proportional to
2
square of the radius of the earth (i.e. g 1/R ). The radius of the earth at the Terai region is less than that
of mountain region as the earth is not a perfect square.

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