Can someone Check this (Energy Question)

[quickslant]

Q: Calculate the total engery of a geosynchonous satellite (one that orbits over a fixed spot) with amass of 1500 kg, orbiting Earth at height 325 km (325 000m) with an orbital speed of 5000 m/s or 5.0x10^3

My Solution: Et = Ep + Ek
Ep = Mg delta H
Ek = 1/2 (m) V^2
thus Et = Mg(H) + 1/2 (m) v^2
(1500)(9.8)(325000) + 1/2(1500) (5000)^2
= 4.78x10^9 + 1.875x10^10
=2.353x10^10 j or 2.353x10^7 Kj

Is there a mistake in my calculations or has this question been done correctly?

 

[PhanthomJay]

Q: Calculate the total engery of a geosynchonous satellite (one that orbits over a fixed spot) with amass of 1500 kg, orbiting Earth at height 325 km (325 000m) with an orbital speed of 5000 m/s or 5.0x10^3

My Solution: Et = Ep + Ek
Ep = Mg delta H
Ek = 1/2 (m) V^2
thus Et = Mg(H) + 1/2 (m) v^2
(1500)(9.8)(325000) + 1/2(1500) (5000)^2
= 4.78x10^9 + 1.875x10^10
=2.353x10^10 j or 2.353x10^7 Kj

Is there a mistake in my calculations or has this question been done correctly?

using g = 9.8m/s/s is valid only near earth. What can you say about GPE at those heights?

 

[quickslant]

i have no idea? is it 0? or is it very small? i have no idea

 

[Doc Al]

Look up the general expression for the gravitational PE between two masses (such as the Earth and a satellite).

As PhanthomJay pointed out, mgh is only useful for finding changes in PE for objects close to the surface of the earth.

 

[quickslant]

ok.. Ep = Gm1m2/r

 

[Doc Al]

ok.. Ep = Gm1m2/r

Don't forget the minus sign: Ep = -Gm1m2/r

 

[quickslant]

ok thank you