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Unformatted text preview: Chapter 4 Additional Notes Earth Example: Here the force that the person feels from the Earth is the same force that the Earth feels from the person. We want the force that the person feels when they are standing at the radius of the Earth. m M E R E F The force the guy feels is then F = G m 1 m 2 r 2 = G M E m R E 2 = 9.8 m / s 2 ( m ) = gm So at the surface of the Earth we can identify g = G M E R E Equilibrium Example: What are the three tensions in the cables? T 3 m = 10 kg T 2 T 1 2 = 53 1 = 37 To find the third tension we will isolate the bottom part of the figure, meaning we will just look at the sign. So we have T 3 m = 10 kg mg y Since it is stationary a=0, so we can write Newtons Second Law as F = T 3 mg = Or solving for the third tension gives T 3 = mg = 98 N To find the other two tensions we will isolate the top part of the diagram, meaning we will only consider the tensions. T 3 T 2 T 1 x y 1 = 37 2 = 53 To solve we consider the directions independently. So we have F x = T 2 cos 2 T 1 cos 1 = F y = T 2 sin 2 + T 1 sin 1 T 3 = For the xdirection For the ydirection In both we have two unknowns, so we will use the xdirection to...
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 Fall '08
 pralle

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