The graph below shows how the force acting on a $1 \mathrm{kg}$ object changes its height above the Earth's surface. How high above the earth's surface would you have to go for the gravitational force to have halved from its original strength on the ground?

 

 

What is the length of time between appearances of Halley's comet?

Is the length of time between two consecutive appearances of Halley's comet always the same?

If Halley's comet was seen in $1066$ and $1682$, how many times would it have been seen between these years?

If Halley's comet was seen $8 \mathrm{times}$ between $1066$ and $1682$, then calculate an average for the length of time between appearances of Halley's comet.

When was Halley's comet last visible? When will it be next to be seen?

Calculate your weight on earth. Take $g=9.8 \mathrm{m} {\mathrm{s}}^{-2}$.

What would your weight be on Mars where $g=3.7 \mathrm{N} {\mathrm{kg}}^{-1}$?

Life on earth has evolved in a uniform gravitational field of  $9.8 \mathrm{N} {\mathrm{kg}}^{-1}$. How might the evolution of life forms be affected by a different gravitational field?