Lesson 6
Rockets!

 Name:ETP Section:M2 Start Time:15:55:36 Instructor:pate Course:355

1) Think about rocket propulsion. Our textbook identifies the product of the rocket's exhaust velocity u ("vex" from Physics 110 days!) and the mass loss rate dm/dt as the Thrust.

In your own words, please briefly explain what each of these quantities (exhaust velocity and mass loss rate) is. Then, think of a non-rocket example in which you could define a "thrust" and identify what each term represents in that example.

2) An aero major friend of yours has designed a rocket and has asked you to take a look at the design. Your friend has programmed the relevant parameters into a Physlet page so that you can better take a look. The physlet shows the rocket launching from the surface of the Earth.

• Use the information provided on the Physlet page (hint: including the elapsed time t) to estimate what the dm/dt of the rocket must be.
Note: To obtain your answer, you'll need 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.

3) A rocket is propelled away from the Earth and runs out of fuel after 120 seconds of flight. Which of these is most likely to be the velocity graph as a function of time (velocity on the y axis, t on the x axis)?

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.):

You may change your mind as often as you wish. When you are satisfied with your responses click the SUBMIT button.

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