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Supposing Newton’s law of gravitation for gravitation forces F1 and F2 between two masses m1 and m2 at positions r1 and r2 read F1 = – F2 = - r_12/r_12^3 GM_0^2 ((m_1m_2)/M_0^2)^n - Physics

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प्रश्न

Supposing Newton’s law of gravitation for gravitation forces F1 and F2 between two masses m1 and m2 at positions r1 and r2 read F1 = – F2 = `- r_12/r_12^3 GM_0^2 ((m_1m_2)/M_0^2)^n` where M0 is a constant of dimension of mass r12 = r1 – r2 and n is a number. in such a case.

  1. the acceleration due to gravity on earth will be different for different objects.
  2. none of the three laws of Kepler will be valid.
  3. only the third law will become invalid.
  4. for n negative, an object lighter than water will sink in water.
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उत्तर

a, c and d

Explanation:

Given, `F_1 = - F_2 = (-r_12)/r_12^3 GM_0^2 ((m_1m_2)/m_0^2)^n`

Acceleration due to gravity, `g = (|F|)/"mass"`

= `(GM_0^2 (m_1m_2)^n)/(r_12^2 (M_0)^(2n)) xx 1/(("mass"))`

 Since. g depends upon the position vector, hence it will be different for different objects. As g is not constant, hence constant of proportionality will not be constant in Kepler's third law. Hence, Kepler's third law will not be valid.

As the force is of central nature.    .....`[∵ "Force" ∝ 1/r^2]`

Hence, the first two of Kepler's laws will be valid.

For negative n, g = `(GM_0^2 (m_1m_2)^-n)/(r_12^2 (M_0)^(-2n)) xx 1/(("mass"))`

= `(GM_0^(2(1 + n)))/r_12^2 ((m_1m_2)^-n)/(("mass"))`

g = `(GM_0^2)/r_12^2 (M_0^2/(m_1m_2)) xx 1/"mass"`

As M0 > m1 or m2

g > 0, hence in this case situation will reverse i.e., an object lighter than water will sink in water.

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अध्याय 8: Gravitation - Exercises [पृष्ठ ६०]

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एनसीईआरटी एक्झांप्लर Physics [English] Class 11
अध्याय 8 Gravitation
Exercises | Q 8.14 | पृष्ठ ६०

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