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7. gravitation — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics7. gravitation1 Mark
MCQ
Every planet revolves around the sun in an elliptical orbit :

$A.$ The force acting on a planet is inversely proportional to square of distance from sun.

$B.$ Force acting on planet is inversely proportional to product of the masses of the planet and the sun

$C.$ The centripetal force acting on the planet is directed away from the sun.

$D.$ The square of time period of revolution of planet around sun is directly proportional to cube of semi-major axis of elliptical orbit.

Choose the correct answer from the options given below :

  • ✓
    $A$ and $D$ only
  • B
    $C$ and $D$ only
  • C
    $B$ and $C$ only
  • D
    $A$ and $C$ only
✓

Answer

Correct option: A.
$A$ and $D$ only
a
$F =\frac{ Gm _1 m _2}{ r ^2}$

$\Rightarrow F \propto \frac{1}{ r ^2}$

$\Rightarrow F \propto m _1 m _2$

$\Rightarrow \text { This force provides centripetal force and acts }$

towards sun

$\Rightarrow T ^2 \propto a ^3 \text { (Kepler's third law) }$

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