If a problem says the acceleration is some positive value than solve using that value, a negative acceleration is said to be deceleration. E.g. a car decelerating at 10 m/sec can be said to be accelerating at -10 m/sec.
If a problem states decelerates at A, then use -A for acceleration in the classic equations which are for acceleration. If a problem says accelerates at a negative value like -A the use -A as the value for acceleration, it can also be said to be decelerating at A.
25,000 Feet = 7620m
PE = mgh where m is mass, g is gravity accel: 9.8 n h is height
= 90 x 9.8 x 7620
= 6720840J
= 6.72MJ
F = ma where m is mass, a is accel = gravity = 9.8
= 90 x 9.8
= 882N
Accel = gravity = 9.8m/s^2
KE = 1/2mv^2 where m is mass n v is vel
if no wind resistance, PE leaving airplane = KE at net
6720840 = 1/2 x 90 x v^2
v^2 = 149352
v = 386.5m/s
150MPH=67m/s
@150MPH, his speed is not changing so accel=0
accel=0, force=0 by newton's second law
force=0 when wind resistance = gravity = 9.8m/s^2
by conservation of energy, Luke's KE = PE = mgh = 6720840J
he was unhurt cuz' his momentum was absorbed by the net
June 21: longest day in Northern Hemisphere
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Answer - Put mixture in a freezer until ice crystals form. Pour off the remaining liquid . The ice can be melted and this process can be repeated to purify the water even more.
Hope this helps :)
Have a great day!
