Answer:
Approximately [tex]4.18 \times 10^{16}\; \rm N[/tex].
Explanation:
Consider two objects of mass [tex]m_{1}[/tex] and [tex]m_{2}[/tex]. Let [tex]r[/tex] denote the distance between the center of mass of each object. Let [tex]G[/tex] denote the gravitational constant. ([tex]G \approx 6.67 \times 10^{-11}\; {\rm m^{3}\cdot kg^{-1}\cdot s^{-2}}[/tex].)
By Newton's Law of Universal Gravitation, the size of gravitational attraction between these two objects would be:
[tex]\begin{aligned}F &= \frac{G\, m_{1}\, m_{2}}{r^{2}}\end{aligned}[/tex].
In this question, [tex]m_{1} = 5.98\times 10^{24}\; {\rm kg}[/tex] and [tex]m_{2} = 6.24 \times 10^{23}\; {\rm kg}[/tex] are the mass of the two planets. The distance between the two planets is [tex]r = 7.83 \times 10^{10}\; \rm m[/tex] (approximately the same as the distance between the center of mass of planet Earth and the center of mass of Mars.)
Apply Newton's Law of Universal Gravitation to find the size of gravitational attraction between the two planets:
[tex]\begin{aligned}F &= \frac{G\, m_{1}\, m_{2}}{r^{2}} \\ &= \frac{1}{(7.83 \times 10^{10}\; {\rm m})^{2}} \\ &\quad \times (6.67 \times 10^{11}\; {\rm m^{3} \cdot kg^{-1} \cdot s^{-2}}) \\ &\quad \times (5.98 \times 10^{24}\; {\rm kg}) \\ &\quad \times (6.42 \times 10^{23}\; {\rm kg}) \\ &\approx 4.18 \times 10^{16}\; {\rm kg \cdot m \cdot s^{-2}} \end{aligned}[/tex].
Since  [tex]1\; {\rm kg \cdot m \cdot s^{-2}} = 1\; {\rm N}[/tex], the size of gravitational attraction between the two planets would be approximately [tex]4.18 \times 10^{16}\; {\rm N}[/tex].
