Aspacecraft is placed in a circular orbit around a planet with mass 6.4 x 1023 kg. the spacecraft orbits at a height of 4.5 x 107 m above the planet’s surface. what additional information is needed to calculate the speed of the spacecraft in the orbit?

It is necessary to know the radius of the planet.  

Explanation:

The speed of the spacecraft can be found by means of the equation of the Universal law of gravity:

 (1)

Where F is the gravitational force, G is gravitational constant, M is the mass of the planet, m is the mass of the spacecraft and r is the orbital radius of the spacecraft.

Equation 1 can be express in terms of the speed by using Newton's second law and the equation for centripetal acceleration:

 (2)

Replacing equation 2 in equation 1 it is gotten:

(3)

the centripetal acceleration is defined as:

 (4)

Replacing equation 4 in equation 3 it is gotten:

(5)

Then, v can be isolated from equation 5:

However, the orbital radius of the spacecraft is obtained by the sum of the radius of the planet and the height of the spacecraft above the surface of the planet (r = R+h)

 (6)

Hence, by equation 6 it can be concluded that it is necessary to know the radius of the planet in order to calculate the speed of the spacecraft.

electrical to thermal

it about 600 mph from what i calculated