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Unformatted text preview: 3) (15 points) Shooting at a fallen branch. A boy decides to test his new slingshot by picking up a rock with a mass of 0.1 kg and
shooting it at a 0.4 kg piece of a fallen tree branch sitting on a frozen pond. Assume that
the branch can slide on the ice without experiencing any frictional forces. a) If the rock is traveling at 10 mfs horizontally just before it hits the branch, how fast
will the combined branch and rock move if the rock gets stuck in the branch upon
impact? 1)) Suppose that the rock broke through a hole in the branch such that after the collision
the rock was moving slower—but in the same direction—as it was just before impact.
Assuming that no pieces of wood broke free from the branch, will the branch 1) not
move? 2) move in the same direction as the rock? or 3) move in the opposite direction as the rock? Please explain your answer. 3) Crane (20 points) In class, We analyzed a "crane" shown at the left. The left
end of the beam is held up by a cable with tension T. The
right end is attached with a frictionless pivoL The mass of
the beam is M, . and can't be ignored. It acts at the center of
the beam. There is an additional mass M: hanging from the
end of the crane. a) Find the tension T in the cable in terms of known quantities b) Find the vertical and horizontal components of the force exerted on the pivot by the
beam. Make sure that the direction of each component is clear! c) Assume the cable suddenly breaks. At the next moment. what is the angular
acceleration of the beam about the pivot? Make sure the direction andfor sign is
clearly deﬁned. ice age'1 45. A U—shaped tube open at both ends contains wateT and a quantity
of oil occupying a 2.0—cm length of the tube, as Shown in
Fig. 15.25. If the oil’s density is 0.82 times that 0f water, what is
the height difference h? EIGHBLILZS Problem 45 Problem 2 \JVV \I \J LA} \_/\ IL.’ \f “JV it? 9. [imam
p
L .. .1
__~__J Figure 2: A volume of material is attached to keep the block submerged 1. What is the minimum force required to keep a cube with density pa and length a fully
eubmurged in a liquid with density .01, if pp < p;'? 2. You are now given some material with density pm > p;. What volume of material would
you need to attach to the cube to keep it fully submurgcd but without sinking to the
bottom? What is its average density of the cube and volume of material together? (What would be
the density of a uniform density block with a mass m = mcube + mmateriq; and a volume V : chbe + Knaterirﬁ?) lli‘Icrcliﬁecl from problem 1?'? of The Portable TA by A. Elby ...
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 Spring '07
 JACOBSEN
 Physics

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