Umm... I think I saw this question somewhere else answered.... You should look for it.
To solve this problem it is necessary to apply the concepts related to the conservation of energy, through the balance between the work done and its respective transformation from the gravitational potential energy.
Mathematically the conservation of these two energies can be given through

Where,
W = Work
Final gravitational Potential energy
Initial gravitational Potential energy
When the spacecraft of mass m is on the surface of the earth then the energy possessed by it

Where
M = mass of earth
m = Mass of spacecraft
R = Radius of earth
Let the spacecraft is now in an orbit whose attitude is
then the energy possessed by the spacecraft is

Work needed to put it in orbit is the difference between the above two


Therefore the work required to launch a spacecraft from the surface of the Eart andplace it ina circularlow earth orbit is

Answer:
We conclude that the centripetal force needed to keep a 7kg mass moving in a circle of 4 meters radius at 15m/s is 393.75 N.
Explanation:
Given
To determine
We need to determine the centripetal force needed to keep a 7kg mass moving in a circle of 4 meters radius at 15m/s.
We know a centripetal force acts on a body to keep it moving along a curved path.
We can determine the centripetal force using the formula

where
is the mass
is the velocity
is the radius
is the centripetal force
substitute m = 7, r = 4, and v = 15 in the formula



N
Therefore, we conclude that the centripetal force needed to keep a 7kg mass moving in a circle of 4 meters radius at 15m/s is 393.75 N.
Answer:
1.25 m/s²
Explanation:
Average acceleration is the change in velocity over change in time.
a = Δv / Δt
a = (5 m/s − 0 m/s) / 4 s
a = 1.25 m/s²