Lesson 4
More Numerical Modeling, Systems of Particles

Name:ETP Section:M2 Start Time:10:36:29 Instructor:pate Course:355

1) Suppose you are in an airplane flying in level flight and you want to drop something out of the plane so that it lands at a particular spot on the ground below (similar to homework problem 2.6!). If there's no drag, you have to drop the object at a certain time in order to hit your target on the ground. If there is drag, do you need to drop later or earlier in order to hit the same spot on the ground? Please explain your reasoning.

Note: To check your answer, and to (hopefully!) help you with your homework problems 2.6 and 2.7, you might want to give another Physlet page a try. Important: This page will open in a NEW window, so you'll need to come back to THIS window (using the taskbar) to submit your preflight. Once again, if the physlet page does NOT load properly, please tell me what happens, including any error messages it displays, in the comments box below. Thanks. Click this link to get to the physlet page.

2) Consider an elevator mechanism that consists of a fixed pulley at the top of the shaft, the elevator, and a counterweight. The elevator (on the right of the figure) and the counterweight are connected by the blue cable shown in the figure. If the blue cable has a breaking tension of about 15000 N and the elevator is supposed to have a maximum capacity of 10 people, what would be a reasonable estimate for the mass of the counterweight?


Numerical modeling methods don't work well when

  1. complicated forces are involved
  2. the acceleration changes rapidly over the Dt used
  3. the motion being modeled is in multiple dimensions
  4. there is no closed form solution to the equations of motion
  5. more than one of the above

Below is a space for your thoughts, including general comments about today's assignment (what seemed impossible, what reading didn't make sense, what we should spend class time on, what was "cool", etc.):

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