Another multiple choice question!!! ok another 2 to be more precise (1 Viewer)

[physician]

( 1 ) An astonaut travels at 72 kph around a horizontal, 10 m radius bend during a training excecise. He experiences 4 g of acceleration when his rocket lifts off. What is the ratio of the training acceleration to that of the rocket.

( A ) 1 : 1

( B ) 1 : 10

( C ) 4g : 4

( D ) 4g : 40


( 2 ) The Earth has a mass of 6.0 * 10²⁴ kg and a radius of 6400 km. A 600 kg satellite experiences a gravitational acceleration of 0.25 m/s² in its orbit. What is the altitude of its orbit?

( A ) 3.36 * 10⁴ km

( B ) 3.36 * 10⁷ km

( C ) 3.97 * 10⁴ km

( D ) 3.97 * 10⁷ km

 

[nick1048]

B and D.....

 

[physician]

B and D.....

do u mind telling me how u worked it out... or at least the formulas u used... because i wasnt sure how to work it out.... thanks anyways for taking the time...

 

[Constip8edSkunk]

1) centripetal acceleration a_c = v² / r
now 72kmph => 72000/3600 = 20m/s
so a_c = 20² /10 = 40ms^-2 , approximately 4g

2) ma = GMm/r²
=> a = GM/r²
=> 0.25 = 6.67 * 10^-11 * 6.0 * 10²⁴ / (6.4 * 10⁶ + h)²
=> h = ((6.67 * 6.0 * 10¹³) / 0.25)^1/2 - 6.4 * 10⁶
= (approx.) 33.6 *10⁷ m = 33.6*10⁴

which is different to nick's ... but it's been a long time since i did this so might have made a mistake somewhere... oh well

edit: html tags didnt work...