Physics Kinetic Energy Question

Quote:

The shuttle craft Galileo from the USS Enterprise encounters a Class M planet. Cmdr. Data decides to orbit the plant 100. m above the surface with a speed of 8.00 x 10^{3} m/s. If the mass of the shuttle-craft is 1.00 x 10^{5} kg.

a) Calculate the gravitational potential energy of the shuttle craft. **(Text book answer: 9.8 x 10**^{7} J)

b) Calculate the bulk kinetic energy of the shuttle craft. **(Text book answer: 1.6 x 10**^{8} J)

c) calculate the total mechanical energy of the system. **(Text book answer: 2.6 x 10**^{8} J)

For part:

a) I got the same answe using the equation E_{g} = mgh = 1.00 x 10^{5} kg * 9.8 m/s^{2} *100.m = **9.8 x 10**^{7} J

b) I tried the using the equation __E___{k} = 0.5mv^{2} and I got an answer of **3.20 x 10**^{12 }J

c) I do not know what to do.

Thank you for your time.

Re: Physics Kinetic Energy Question

Quote:

Originally Posted by

**sakonpure6** For part:

a) I got the same answe using the equation E_{g} = mgh = 1.00 x 10^{5} kg * 9.8 m/s^{2} *100.m = **9.8 x 10**^{7} J

b) I tried the using the equation __E___{k} = 0.5mv^{2} and I got an answer of **3.20 x 10**^{12 }J

c) I do not know what to do.

Thank you for your time.

a) The question is poorly formed as nowhere are we given the gravitational acceleration of the planet or at least it's mass. We need at least one of them in order to be able to calculate the potential energy of the shuttle. You've assumed that it's the same as Earth, i.e. 9.8 m/s. You should at least state that you've made that assumption. If you were given the radius of the planet you could calculate what it's gravitational acceleration is, assuming a zero thrust orbit, but you're not given this either.

b) I get the same answer as you do.

c) total mechanical energy is just the sum of potential and kinetic energy.