Chapter 13 - Gravitation - Problems - Exercises - Page 431: 13.83

(c) about 1.5g

Let m and r be the mass and radius of the earth, respectively, while M and R are the mass and radius of the exoplanet. We are given $M = 7.9m$ and $R = 2.3r$. Using $g = \frac{GM}{r^{2}}$, we get – $g' = G\frac{(7.9m)}{(2.3r)^{2}} = \frac{(7.9)}{(2.3)^{2}}G\frac{m}{r^{2}} = 1.49338374g \approx 1.5g$