Lesson_4.5_Homework_Solution

# Lesson_4.5_Homework_Solution - Lesson 4.5 Homework...

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Lesson 4.5 Homework Solutions 1. What is the value g on the surface of a planet that has twice the mass of the earth and a radius 1.5 times the radius of the earth? If g is the acceleration due to gravity on earth and g’ the acceleration due to gravity on the other planet, we have 2 2 2 2 2 2 2 2 ' (1.5 ) 2.25 2.25 2.2 0 5 .89 e e e e e e e e G GM g R G M GM g g R R g M R = = = = = = 2. Calculate the force of gravity on a spacecraft 8000 km from the surface of the earth if its mass is 1600 kg. If g is the acceleration due to gravity on earth and g’ the acceleration due to gravity at the spacecraft, we have ( 29 2 2 2 6 2 2 2 6 6 2 ' ( ) ' (6.38 10 ) 0.2 ( ) 6.38 10 8 10 ' 0.2 1.96 e e e e e e GM g R GM g R h g R g R h g g ms - = = + × = = = + × + × = = Force of gravity on the spacecraft = mg’ = 1600 × 1.96 = 3136 N 3. What is the value of g at an altitude of 450 km above the surface of the earth? Let g’ be the acceleration due to gravity at an altitude h = 450 km 2 2 2 6 2 14 6 5 2 -2 13 ' ( ) ( ) 9.8 (6.38 10 ) 3.99 10 ' (6.38 10 4.5 10 8.56 m ) 6 1 s 4. 6 0 e e e e GM gR g R h R h g = = + + × × × = = = × + × ×

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4 . The average distance of Neptune from the sun is 4.5 x 10 9 km. Using the fact that the earth is 1.5 x 10 8 km from the sun, compute the length of Neptunian year. T n – Period of Neptune, T e – Period of earth, r n – average distance of Neptune from the sun, r e – average distance of earth from the sun. 2
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## This note was uploaded on 05/01/2011 for the course PHY 2048 taught by Professor George during the Fall '10 term at Edison State College.

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Lesson_4.5_Homework_Solution - Lesson 4.5 Homework...

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