Question

Find the weight of an object at neptune which weighs $19.6N$ on the earth. Mass of Neptune $={10}^{26}kg$, radius $R=2.5\times {10}^{4}km$ and rotates once around its axis in $16h.$

• A. $19.6N$
• B. $20.0N$
• C. $20.4N$
• D. $20.8N$

Answer 1

The correct option is D $20.8N$

$WeightW=\frac{GMm}{R^2}$
$=\frac{6.67\times {10}^{-11}\times {10}^{26}\times 2}{(2.5\times {10}^7{)}^2}=20.8N$.