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A body weighs [tex][tex]$63 N$[/tex][/tex] on the surface of the Earth. What is the gravitational force on it due to the Earth at the height of [tex]3200 \, \text{km}[/tex] from the Earth's surface? (Radius of the Earth is [tex]6400 \, \text{km}[/tex].)

[Ans: [tex]28 N[/tex]]


Sagot :

Certainly! Let's solve this problem step-by-step.

1. Understanding the Scenario:
- The weight of the body on the surface of the Earth is [tex]\( 63 \, \text{N} \)[/tex].
- The height above the Earth's surface where we want to find the new gravitational force is [tex]\( 3200 \, \text{km} \)[/tex].
- The radius of the Earth is given as [tex]\( 6400 \, \text{km} \)[/tex].

2. Determine the Distances:
- Distance from the center of the Earth to the surface is the radius of the Earth: [tex]\( r_{\text{surface}} = 6400 \, \text{km} \)[/tex].
- Distance from the center of the Earth to the point 3200 km above the surface:
[tex]\[ r_{\text{above}} = r_{\text{surface}} + \text{height above surface} = 6400 \, \text{km} + 3200 \, \text{km} = 9600 \, \text{km} \][/tex]

3. Using the Concept of Gravitational Force:
- The gravitational force varies inversely with the square of the distance from the center of the Earth. This relationship is given by:
[tex]\[ F_{\text{above}} = F_{\text{surface}} \left( \frac{r_{\text{surface}}}{r_{\text{above}}} \right)^2 \][/tex]
- Where:
[tex]\[ F_{\text{surface}} = 63 \, \text{N} \quad \text{(gravitational force at the surface)} \][/tex]

4. Plug in the Values:
[tex]\[ F_{\text{above}} = 63 \, \text{N} \left( \frac{6400 \, \text{km}}{9600 \, \text{km}} \right)^2 \][/tex]

5. Calculate the Fraction:
- Simplify the fraction [tex]\( \frac{6400}{9600} \)[/tex]:
[tex]\[ \frac{6400}{9600} = \frac{2}{3} \][/tex]

6. Square the Fraction:
[tex]\[ \left( \frac{2}{3} \right)^2 = \frac{4}{9} \][/tex]

7. Calculate the Gravitational Force at the Height:
[tex]\[ F_{\text{above}} = 63 \, \text{N} \times \frac{4}{9} = 63 \, \text{N} \times 0.4444 = 28 \, \text{N} \][/tex]

Therefore, the gravitational force on the body at a height of [tex]\( 3200 \, \text{km} \)[/tex] above the Earth's surface is [tex]\( 28 \, \text{N} \)[/tex].