Question

Find the weight of an object at Neptune which weighs 19.6 N on the earth. Mass of Neptune = 10²⁶ kg, radius R = 2.5 × 10⁴ km and rotates one around its axis in 16 h.

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

Answer 1

Answer: (D)

20.8 N

Answer 2

Weight W = $\frac{GMm}{R^{2}}$

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