Orbits of Satellites Quick Check

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Question
Let G be the universal gravitational constant and mp be the mass of the planet a satellite is orbiting. Which equation could be used to find the velocity of the satellite if it is placed in a low Earth orbit?(1 point)
Responses

v=1(200 km)Gmp−−−−√
v is equal to the fraction with numerator 1 and denominator right paran 200 kilometers left paran end fraction square root of cap g m sub p end root

v=Gmp(200 km)−−−−−−√
v is equal to square root of the fraction with numerator cap g m sub p and denominator right paran 200 kilometers left paran end root

v=1(7,000 km)Gmp−−−−√
v is equal to the fraction with numerator 1 and denominator left bracket 7 comma 000 kilometers right bracket end fraction square root of cap g m sub p end root

v=Gmp(7,000 km)−−−−−−−√
v is equal to square root of the fraction with numerator cap g m sub p and denominator left bracket 7 comma 000 kilometers right bracket end root

1 answer

To find the velocity of a satellite in a circular orbit around a planet, we can use the formula derived from setting the gravitational force equal to the centripetal force required to keep the satellite in orbit.

The formula for the orbital velocity \( v \) is given by:

\[ v = \sqrt{\frac{GM_p}{r}} \]

where:

  • \( G \) is the universal gravitational constant,
  • \( M_p \) is the mass of the planet,
  • \( r \) is the distance from the center of the planet to the satellite.

In the case of a low Earth orbit, if we assume the radius \( r \) is approximately equal to the radius of the Earth plus the altitude of the orbit (which may be about 200 km), we usually represent this in kilometers.

Given the options you provided, the correct formula aligns with:

\[ v = \sqrt{\frac{G M_p}{(R_{Earth} + h)}} \]

For a low Earth orbit (considering \( R_{Earth} \) to be approximately 6,371 km and the orbit being 200 km above the surface, we have \( r \approx 6,571 \) km), the equation that fits the forms you provided is:

\[ v = \sqrt{\frac{G M_p}{200 \text{ km}}} \]

However, since the radius needs to be expressed in the formula, the correct choice among your options would be:

v = \( \sqrt{ \frac{G M_p}{200 \text{ km}}} \)

So the answer among the responses you provided closely resembles:

v = \( G M_p (200 \text{ km})^{-1/2} \)

However, none of the provided options truly match the correct structure with \( G \) and \( M_p \). Hence, verify if there's a misrepresentation, as the units and structure for gravitational formulas need to align with the square root form accurately.