A 7340 kg satellite has an elliptical orbit, as in Figure 6.9b. The point on the

Question

A 7340 kg satellite has an elliptical orbit, as in Figure 6.9b. The point on the orbit that is farthest from the earth is called the apogee and is at the far right side of the drawing. The point on the orbit that is closest to the earth is called the perigee and is at the far left side of the drawing. Suppose that the speed of the satellite is 2770 m/s at the apogee and 8150 m/s at the perigee

(a) Find the work done by the gravitational force when the satellite moves from the apogee to the perigee. in J
(b) Find the work done by the gravitational force when the satellite moves from the perigee to the apogee. in J

Thank yall very much for your help. This is the only problem that I cant solve on my own and the prof has not showed us how to do this. Thanks a million!!!!

Explanation / Answer

Work Energy Theorem;
Work done by all forces on an object = object's change in Kinetic Energy

In this problem the only force on the satellite is gravity. So work done by gravity = change in KE;

Work = KE(perigee) - KE(apogee)

= (1/2)7340)(8150)^2 - (1/2)(7340)(2770)^2

= 2.156 x 10^11 Joules

(b) just switch the order to KE(apogee) - KE(perigee) to get;

Work = - 2.156 x10^11 Joules

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