pt5 - Name: Section: Practice Test 5 for Test 3 Assignment...

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Name: Section: Practice Test 5 for Test 3 Assignment Due:Wednesday 4-2-2008 Practice Test Problem 5.1 You need to send your broken telescope back the the Meade factory, and you decide to ship it FedEx. Your telescope (in its case) is placed on top of a cargo container inside a FedEx plane. The telescope’s inertia is 55kg , the inertia of the cargo container is 225kg , and the plane’s inertia is 15 , 000kg (small cargo plane). During the ±ight, the airplane experiences (unbelievably) no turbulence, but ±ies straight and level for the entire ±ight. Parts (a), (b) and (c) ask you to draw free-body diagrams. Label the forces using the F type by,on notation. Make sure the length of the force vectors are appropriate for the magnitudes of the forces. Make a note if you need to draw vectors to a di²ering scale. (a)[5 pt(s) ]Draw the free-body diagram for your telescope (t). (b)[6 pt(s) ]Draw the free-body diagram for the cargo container (c). (c)[6 pt(s) ]Draw the free-body diagram for the FexEx plane (p). (d)[2 pt(s) ]Identify all interaction pairs, and write them out. (e)[4 pt(s) ]Find the magnitude of all the forces on your telescope. Show your work. (f)[5 pt(s) ]Find the magnitude of all the forces on the cargo container. Show your work. (g)[5 pt(s) ]Find the magnitude of all the forces on the FedEx plane. Show your work. (h)[2 pt(s) ]In which direction would the plane need to accelerate to cause the telescope to “weigh” more than it does at rest? Practice Test Problem 5.2 You wish to design a children’s toy that hops unexpectedly. You put a strong spring inside a plastic housing so that it is vertical. The plastic housing has a rubber gasket that provides a weak suction seal with a rubber base you apply to the base end of the spring. When you squeeze it together, the spring is compressed. At an unpredicted moment, the suction seal breaks and the toy pushes on the ±oor with an average force of 10 times the weight of the 0 . 15kg toy. The center of mass of the toy is 2 . 0cm o² the ground when the spring is compressed. The center of mass is 5 . 0cm o² the ground when the toy can no longer push against the ±oor. (Since I used the word average, you can assume the force due to the spring is constant, even though we know it would actually change as the spring relaxed.) (a)[5 pt(s) ]If you were to identify just the toy as your system, what is the net external force on the toy as it is jumping? Draw a free body diagram for the toy. (b)[3 pt(s) ]Assuming the toy was at rest when the seal broke, what is its kinetic energy when it leaves the ±oor? (c)[8 pt(s) ]How much work did the ±oor do on the toy? Carefully draw a work-energy diagram showing how energy was transferred during the jump for the de³ned system. (d)[4 pt(s)
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pt5 - Name: Section: Practice Test 5 for Test 3 Assignment...

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