Thursday

December 18, 2014

December 18, 2014

Posted by **marie** on Friday, October 8, 2010 at 6:56am.

- physics -
**drwls**, Friday, October 8, 2010 at 7:00amWhat are the units of the "190" elevation from which it fell?

29.5 Km is not a measure of energy. Please copy the question more carefully

- physics -
**marie**, Friday, October 8, 2010 at 7:02am190Km *

29.5 MJ *

- physics -
**drwls**, Friday, October 8, 2010 at 9:15amThe gravitational potential energy change is

deltaPE = -G*M*m/R + G*M*m/(R+h)

where G is the universal gravity constant, M is the mass of the earth, m is 170 kg and R is the radius of the earth (6,378,000 m). h is the initial altitude above the Earth's surface.

This can also be written

deltaPE = -mgR + mgR[R/(R+h)]

= -mgR{1 - [1/(1 + h/R)]}

= -170kg*9.8 m/s^2*6378*10^3 m

*{1 - [1 - 1/(1 + (190/6378))]

= -1.063*10^10*0.0289 = -3.071*10^8 J

So 307 MegaJoules of gravitational PE is lost. If the kinetic energy on arrival is 29.5 mJ, the remainder has been lost due to frictkion, and converted to heat.

- physics -
**marie**, Friday, October 8, 2010 at 2:17pmthank you, but for some reason its wrong

- physics -
**marie**, Friday, October 8, 2010 at 2:18pmit says "Make sure you calculate with at least 3 significant digits. Express your answer using two significant figures."

- physics -
**Anonymous**, Friday, October 8, 2010 at 4:09pmThe above equation is all right -- just make sure you use the right value for mass (72 kg; not 170). Also, make sure you convert the 190km into meters--therefore your calculations would be (190,000m/6.4e6m). If you do all the conversions right, you should get the right answer! Good luck.

**Answer this Question**

**Related Questions**

PHYSICS FINAL (orbital) - A 3300kg satellite is traveling 3550 km above the ...

physics - Calculate the velocity needed for an object starting at the Earth's ...

PLEASE HELP FINAL PROBLEM ORBITAL - A 3300kg satellite is traveling 3550 km ...

PHYSICS HELP - A satellite of mass m is orbiting the earth, mass M , in a ...

gravity - You are an astronaut in the space shuttle pursuing a satellite in need...

Physics Classical Mechanics - A satellite of mass m is orbiting the earth, mass ...

physics - Two satellites are in circular orbits around the earth. The orbit for ...

physics 1 - Two satellites are in circular orbits around the earth. The orbit ...

Physics - A 13 kg asteroid is traveling through space with velocity v = 110 m/s ...

phy101 - Calculate the velocity needed for an object starting at the Earth's ...