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QJEEM23Phca88: JEE Main 2023 Physics - Class 11 JEEM23Phca88 Solution: The escape velocities of two planets and are in the ratio . If…

The escape velocities of two planets A\mathrm{A} and B\mathrm{B} are in the ratio 1:21: 2 . If the ratio of their radii respectively is 1:31: 3 , then the ratio of acceleration due to gravity of planet A to the acceleration of gravity of planet B will be :

Multiple Choice Options

  • A 43\frac{4}{3}
  • B 23\frac{2}{3}
  • C 34\frac{3}{4}
  • D 32\frac{3}{2}

Step-by-Step Verified Solution

The escape velocity of a planet is given by the formula:

vescape=2GMR\mathrm{v}_{\text{escape}} = \sqrt{\frac{2GM}{R}}

where G is the gravitational constant, M is the mass of the planet, and R is its radius.

If the escape velocity of planet A is vA and the escape velocity of planet B is vB, then we can write the following relationship:

vBvA=2GMBRB2GMARA=RAMBMARB{{{v_B}} \over {{v_A}}} = {{\sqrt {{{2G{M_B}} \over {{R_B}}}} } \over {\sqrt {{{2G{M_A}} \over {{R_A}}}} }} = \sqrt {{{{R_A}{M_B}} \over {{M_A}{R_B}}}}

⇒\Rightarrow RAMBMARB=2\sqrt {{{{R_A}{M_B}} \over {{M_A}{R_B}}}} = 2

⇒\Rightarrow MBMA×13=4{{{M_B}} \over {{M_A}}} \times {1 \over 3} = 4

⇒\Rightarrow MBMB=12{{{M_B}} \over {{M_B}}} = 12

We know, The acceleration due to gravity on a planet can be calculated using the formula:

g=GMR2\mathrm{g} = \frac{\mathrm{G} \mathrm{M}}{\mathrm{R}^2}

where G is the gravitational constant, M is the mass of the planet, and R is its radius.

gAgB=MARB2MBRA2=112×(31)2=912=34{{{g_A}} \over {{g_B}}} = {{{M_A}R_B^2} \over {{M_B}R_A^2}} = {1 \over {12}} \times {\left( {{3 \over 1}} \right)^2} = {9 \over {12}} = {3 \over 4}

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