A person whose mass is 100 kg travels from Earth to Mars in a spaceship. Neglect all other objects in sky and take acceleration due to gravity on the surface of the Earth and Mars as $10\ \text{m s}^{-2}$ and $4\ \text{m s}^{-2}$, respectively. Identify from the below figures, the curve that fits best for the weight of the passenger as a function of time.
Answer: (A) (c)
The weight starts at $100\times10 = 1000$ N on Earth and falls rapidly as the distance from Earth grows. At the neutral point the pulls of Earth and Mars cancel and the weight is zero. Beyond it the pull of Mars dominates and the weight rises to $100\times4 = 400$ N on Mars.
Weight is a magnitude, so it never becomes negative. Curve (c), which touches zero once and then rises to 400 N, fits best.
Solution by Sreeraj P, M.Sc Physics