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Unformatted text preview: Solution for Practice Test 5 for Test 3 Solution to Practice Test Problem 5.1(telescope FBD) Problem: 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 telescopes inertia is 55kg , the inertia of the cargo container is 225kg , and the planes inertia is 15 , 000kg (small cargo plane). During the flight, the airplane experiences (unbelievably) no turbulence, but flies straight and level for the entire flight. 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 differing scale. (a)Draw the free-body diagram for your telescope (t). (b)Draw the free-body diagram for the cargo container (c). (c)Draw the free-body diagram for the FexEx plane (p). (d)Identify all interaction pairs, and write them out. (e)Find the magnitude of all the forces on your telescope. Show your work. (f)Find the magnitude of all the forces on the cargo container. Show your work. (g)Find the magnitude of all the forces on the FedEx plane. Show your work. (h)In which direction would the plane need to accelerate to cause the telescope to weigh more than it does at rest? Solution to Part (a) The telescope experiences two forces, the force of gravity acting on the tele- scope, and the contact force of the cargo container on the telescope. The telescope is not accelerating, so these forces balance. Note that since the forces balance, these two forces have the same magnitude. F c c,t F g e,t a = 0 Grading Key: Part (a) 5 Points 1 point(s) (2 times) : Each force correctly labelled. 1 point(s) : Zero acceleration indicated. 1 point(s) : Forces same size. 1 point(s) : Forces have correct direction. Solution to Part (b) 1 The cargo container experiences three forces: the force of gravity acting on the container, the contact force of the telescope acting on the container, and the contact force of the plane acting on the cargo container. The container is not accelerating, so the forces balance. The contact force of the telescope on the container pairs with the force of the container on the telescope from the previous part. This gives us a scaling for the diagram. Since the mass of the container is roughly four times that of the telescope, the force of gravity on the container should be four times larger than the contact force of the telescope on the cargo container. The force the plane exerts on the container must be equal and opposite to the sum of the downward forces....
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- Spring '08