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aaronrusso

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posted by aaronrusso on 11/5/2009 2:40:26 AM | status: Live | Earned Karma: 0

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I need help with some physics problems ASAP...only have less than 24 hours left

Course	Textbook	Chapter	Problem	Needs by
N/A	N/A	N/A	N/A	11/5/2009 at 2:00:00 PM

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1) A boat moves upstream 25.6 nautical miles (nm) at 9.6 knots (as measured by a speedometer on the boat) against a 2.2 knot current. The boat then travels 25.6 nm downstream at 9.6 knots with the current. How does the elapsed time for the entire trip compare to the time for a 51.2 nm trip at 9.6 knots across a still lake?
1 hours difference

2) The gravitational force between the earth and an object of mass m = 24 kg, close to the surface of earth, is given by
$F^^\-> =-(G_N M_E m)/(R_E)^2 r^^\^ ,$
where $r^^\^$ is a unit vector that points radially outwards from the center of the earth. Newton's gravitational constant, mass of earth and radius of earth's surface are respectively
G_N = 6.67 cross 10^(-11) (text(m)^3)/(text(kg) middot text(s)^2)

G_N = 6.67 cross 10^(-11) (text(m)^3)/(text(kg) middot text(s)^2)

(a) $(F^^\->)/(m) =$ 1 $r^^\^$ (text(m))/(text(s)^2)

(b) How much work has to be done by you to lift this mass to a height of 1.6 m above the surface of earth. Note that the work done by you is negative of the dot product of the gravitational force and displacement.
2 (text(kg)*text(m)^2)/(text(s)^2)

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