A research satellite of mass 200 kg circles the earth in an 3R orbit of average radiuswhere R is the radius of earth. Assuming the gravitational pull on a mass of 1 kg on the earth's surface to be 10 N, the pull on the satellite will be (a) 880 N (c) 885 N (b) 889 N (d) 892 N

Respuesta :

Answer: (b) 889N

The given options do not match with the given data. However, working with an orbit of radius 3R/2 the answer is 889N.

Explanation:

According to Newton's law of Gravitation, the force [tex]F[/tex] exerted between two bodies of masses [tex]M[/tex] and [tex]m[/tex]  and separated by a distance [tex]R[/tex]  is equal to the product of their masses and inversely proportional to the square of the distance:

[tex]F=G\frac{Mm}{R^2}[/tex]

Where [tex]G[/tex]is the gravitational constant, [tex]M[/tex] is the mass of the Earth in this case

.

If we are told the gravitational pull on a mass of [tex]m_{1}=1 kg[/tex]on the earth's surface to be 10 N, this means the force at the surface is:

[tex]F=10N=G\frac{Mm}{R^2}[/tex]   (1)

Assuming the mass of the Earth and its radius constant that we will name [tex]g[/tex], we can say:

[tex]G\frac{M}{R^2}=g[/tex]   (2)

Then:

[tex]10N=g.m_{1}=g.(1kg)[/tex]   (3)

Finding [tex]g[/tex]:

[tex]g=\frac{10N}{1kg}=10m/s^2[/tex]  (4)

Now, the gravitational pull at a certain height [tex]h[/tex] over the surface is:

[tex]F_{h}=G\frac{Mm_{2}}{{(R+h)}^2}[/tex]  (5)

Where [tex]m_{2}[/tex] is the mass of the satellite.

If we are told the radius of the orbit of the research satellite is [tex]3R/2[/tex], this means [tex]R+h=3R/2[/tex]:

[tex]F_{h}=G\frac{Mm_{2}}{{(3R/2)}^2}=G\frac{M}{R^2}.\frac{4m_{2}}{9}[/tex]   (7)

Substituting (4) in (7):

[tex]F_{h}=g\frac{4m_{2}}{9}[/tex]   (8)

Knowing the mass of the research satellite is 200kg:

[tex]F_{h}=10m/s^2\frac{(4)(200kg)}{9}[/tex]  (9)

Finally:

[tex]F_{h}=888.888N\approx 889N[/tex]  This is the gravitational pull on the satellite with an orbit of radius 3R/2