Verified Solution • 2025–26 Session moderate

QNEET-2024-Ph-75: NEET 2024 Physics - Class 11 NEET-2024-Ph-75 Solution: The mass of a planet is \( {1}{10}\)th that of the earth and…

The mass of a planet is 110\frac{1}{10}th that of the earth and its diameter is half that of the earth. The acceleration due to gravity on that planet is: 19.6 m s−219.6\ \text{m s}^{-2} 9.8 m s−29.8\ \text{m s}^{-2} 4.9 m s−24.9\ \text{m s}^{-2} 3.92 m s−23.92\ \text{m s}^{-2}

Multiple Choice Options

  • A 19.6 m s−219.6 \mathrm{~m} \mathrm{~s}^{-2} 19.6   m   s _ 2
  • B 9.8 m s−29.8 \mathrm{~m} \mathrm{~s}^{-2} 9.8   m   s _ 2
  • C 4.9 m s−24.9 \mathrm{~m} \mathrm{~s}^{-2} 4.9   m   s _ 2
  • D 3.92 m s−23.92 \mathrm{~m} \mathrm{~s}^{-2} 3.92   m   s _ 2

Step-by-Step Verified Solution

The acceleration due to gravity (g) on a planet is given by the formula: g = G M R 2 where: G GG G is the universal gravitational constant, M MM M is the mass of the planet, and R RR R is the radius of the planet. In this question, we know that: The mass of the planet M p MpM_p M p _ is 1 10 110\frac{1}{10} 10 1 _ of the mass of the earth M e MeM_e M e _ , so M p = M e 10 Mp=Me10M_p = \frac{M_e}{10} M p _ = 10 M e _ _ . The diameter of the planet is half that of earth. Since the diameter is twice the radius, a diameter half that of earth implies the radius R p RpR_p R p _ is also half the radius of the earth R e ReR_e R e _ . Therefore, R p = R e 2 Rp=Re2R_p = \frac{R_e}{2} R p _ = 2 R e _ _ . Using the formula for acceleration due to gravity and substituting the above information: g p = G M p R p 2 = G M e 10 ( R e 2 ) 2 Simplify the expression: g p = G M e 10 _ 4 R e 2 = 4 10 G M e R e 2 Knowing that G M e R e 2 GMeRe2G \frac{M_e}{R_e^2} G R e 2 _ M e _ _ is the acceleration due to gravity on Earth g e � 9.8 m / s 2 ge≈9.8 m/s2g_e \approx 9.8 \, \mathrm{m/s}^2 g e _ � 9.8 m/s 2 , we substitute this value into the equation: g p = 4 10 _ 9.8 m / s 2 = 3.92 m / s 2 Thus, the acceleration due to gravity on the planet is 3.92 m / s 2 3.92 m/s23.92 \, \mathrm{m/s}^2 3.92 m/s 2 , which corresponds to: Option D: 3.92   m / s 2

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