Calculating Force of Attraction between Earth and 3.0 kg Mass

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SUMMARY

The discussion focuses on calculating the gravitational force of attraction between Earth and a 3.0 kg mass using Newton's law of gravity. The formula used is F = G(m1 * m2) / r^2, where G is the gravitational constant (6.67 x 10^-11 Nm²/kg²), m1 is the mass of Earth (5.98 x 10^24 kg), and r is the distance from the Earth's center (6,370,000 meters). A common error identified was converting kilograms to grams, which led to incorrect calculations. The correct gravitational force should be approximately 29.4 N, aligning with the acceleration due to Earth's gravity (10 m/s²).

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Homework Statement



Calculate, using Newton's law of gravity, the size of the force of attraction between the Earth and a mass of 3.0 kg on the Earth. Data: Distance to the center of Earth from the surface = 6370 km. Mass of Earth = 5.98 1024 kg. Gravitational constant (G = 6.67 times 10-11 Nm2/kg2).


Homework Equations



F = G(m1 * m2)/ r^2

The Attempt at a Solution



I plugged the numbers into the equation and converted km to meters and kg to g ...

6.67E-11 * (3000)(5.98E27) / (6370000)^2
and I got 2.949E-7, but it is wrong I think
 
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The answer is quite a way off.

1.Why did you convert Kg to g? The SI unit of mass is Kg. When you substitute 6.67e-11 for G, it means G = 6.67e-11 Nm2/Kg2. So make sure the units are uniform throughout.

2.You can make a rough estimate of the answer. If you've come across the term acceleration due to Earth's gravity(g), you may know that it is roughly equal to 10ms-2. The weight of an object on the Earth, which is nothing but the gravitational force due to the Earth, is mg, where m is the mass of the object.
 

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