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NEWTON’S 2ND LAW =
Units=
6 &
7 Dr. John P. Csie, Professor of Physics, Austin com. College, 1212 Rio Gra=
nde
St., Austin Tx 78701 jpcise@austincc.edu & NYTimes June 5, 2010 by Kenneth Ch=
ang. Send
an e-mail on use you got. Thanks! Dr Cise
INTRO=
DUCTION:=
Forces on the Falcon 9 for the first 75 s are as shown in graphic at le=
ft. QUEST=
IONS:=
(a) Find the mass(in slugs) of=
Falcon 9? (b) Find the net force on Falcon 9=
? (c) Using Newton’s second law find the
acceleration of Falcon 9 during the first 75 s? (d) Find Falcon 9’s speed after 75 s?<=
o:p> ANSWE=
RS:=
(a) ~
22,969 slugs (b) ~ 390,000 lb (c) ~ 17 ft/s2 (d) ~ 1273 ft/s COMME=
NT:=
In the literature it is stated=
that After 75 s the Falcon 9 is traveling at just=
over
the speed of sound (1125 ft/s). Note Our answer checks out with what is stated. <=
o:p>
The Space Exploration Technologies Corporation= a>, SpaceX for short, launched the 154-foot, 735,000-pound Falcon 9 rocket from the Cape Canaveral Air Force Station in Florida, heading east over the Atlantic. The nine first-stage engines ignited at 2:45 p.m. and burned for three minutes before dropping into the ocean while the second-stage engines burned about six minutes to place a dummy payload caps= ule almost perfectly into the target orbit 155 miles above the Earth. “We achieved 100 percent of o= ur objectives on the mission,” said Elon Musk, SpaceX’s founder and chief executive. The launching was pushed back almost four hours after the countdown hit a few snags, including a delay to fix a problem in the rocket= ’s self-destruct system and a last-minute abort, at 1:30 p.m., because of an engine reading outside the acceptable range. SpaceX engineers reset the sys= tems and resumed the countdown before the launching window closed at 3 p.m. The success was a major boon to those supporting P= resident Obama’s proposal to turn the launching of astronauts over = to private companies. A spectacular failure would have provided ammunition to opponents who call Mr. Obama’s approach too risky.