Physics Help Forum help needed...hmm...

 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum

 Oct 7th 2009, 09:10 AM #1 Senior Member   Join Date: Sep 2009 Location: St. John's, NL Posts: 124 help needed...hmm... A spacecraft moves in a circular orbit with a speed of 7.77 km/s with a period of 88.9 min. What is the radius of the spacecraft's orbit? what is the radial acceleration of the satellite? Then, in order to begin its re-entry, the spacecraft engines are fired to provide an acceleration of 5.20 m/s2 in a direction opposite to its velocity. What is the magnitude of the spacecraft's total acceleration just after the engines begin to fire. hmm... can someone explain me how to solve this problem? thank you for reading !!
 Oct 7th 2009, 09:23 AM #2 Banned   Join Date: Aug 2009 Location: UK Posts: 240 Forum rules state that you must show some attempt? where are you stuck?
 Oct 7th 2009, 09:33 AM #3 Senior Member   Join Date: Sep 2009 Location: St. John's, NL Posts: 124 i don't know how to do... that's why i am asking HOW TO SOLVE not the answer... but i will delete it if its against rules ! thank you
 Oct 7th 2009, 10:14 AM #4 Banned   Join Date: Aug 2009 Location: UK Posts: 240 A spacecraft moves in a circular orbit with a speed of 7.77 km/s with a period of 88.9 min. What is the radius of the spacecraft's orbit? what is the radial acceleration of the satellite? Then, in order to begin its re-entry, the spacecraft engines are fired to provide an acceleration of 5.20 m/s2 in a direction opposite to its velocity. What is the magnitude of the spacecraft's total acceleration just after the engines begin to fire. 88.9 min x 60 = 5334 secs 7.77 km/s x 5334 = 41445.18 km circumference. 41445.18 / (2pi) = 6596.2 km radius radial acceleration also known as centripetal acceleration = V^2/ radius i'll let you work the rest out.
 Oct 7th 2009, 03:46 PM #5 Senior Member   Join Date: Sep 2009 Location: St. John's, NL Posts: 124 thank you ! i got the radial accerlation. how do i do the "In order to begin its re-entry, the spacecraft engines are fired to provide an acceleration of 5.20 m/s2 in a direction opposite to its velocity. What is the magnitude of the spacecraft's total acceleration just after the engines begin to fire." one? radial accerlation is 9.15 m/s^2 so i did 9.15 - (-5.20) but its wrong... hmm 9.15 - 5.20
 Oct 8th 2009, 08:05 AM #6 Senior Member   Join Date: Sep 2009 Location: india Posts: 409 i found the acc 10.53m/s^2. method used= the radial acc came what you found out=9.16m/s^2. THIS ACC IS TOWARDS THE CENTRE AND THE ACC PUT IN EFFECT BY ENGINE IS OPPOSITE TO SHUTTLE VELOCITY. VELOCITY OF SHUTTLE IS ALWAYS ALONG THE TANGENT. SO 5.20 ACC ACTS IN A DIRECTION PERPENDICULAR TO THE RADIAL ONE. so a (total)=root over(5.20^2+9.16^2)=10.53 acc=acceleration.
 Oct 8th 2009, 12:08 PM #7 Senior Member   Join Date: Sep 2009 Location: St. John's, NL Posts: 124 got it after. thank you !!

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