Gravity on Mars (Better)

Question:

Mars and Earth have diameters of 6775 and 12775 km respectively. The mass of Mars is 0.107 times that of Earth. If a body weighs 200N on Earth, what would it weigh on Mars? Also, what is the mass of the body and the gravitational acceleration on Mars?

Answer:

The acceleration due to gravity at the surface of a planet varies directly as the mass and inversely as the square of the radius. This folllows directly from Newton's law of universal gravitation. This makes the gravitational acceleration on Mars gm=9.8*0.107*(12775/6775)2 = 3.73m/s/s.

The weight of an object is its mass (m)times the acceleration of gravity. So 200=9.8*m or m=20.41kg. This mass is of course the same on Mars so the weight on Mars is Wm=3.73*20.41=76.1N

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