Lesson 27
Collisions and Scattering; Elastic Collisions of Two Particles

Name:faculty Section:M2 Start Time:14:38:50 Instructor:pate Course:355

1) Section 9.6 in Marion and Thornton has an interesting way of presenting different types of 2d elastic collisions. In particular, consider Figure 9-11 on page 353. This figure may be a bit hard to understand at first glance. In your own words, please explain what the difference is between Figure 9-11(a) and Figure 9-11(b). When can each case occur? Please try to think of an example that would fit figure (a) and another example that would fit figure (b). When you give your example, feel free to include example numbers (e.g., for the masses, speeds, angles, etc.).

2) It is possible to tell a lot about the objects that undergo a 2d collision just by examining the paths they take. (This is yet another 'cool' thing about physics!)

Suppose, for example, you have two objects undergoing a 2d elastic collision. You can infer a ratio of masses of the objects by examining the paths. Use the physlet to estimate the ratio of the black mass to the red mass. Please explain what you do in order to come up with your estimate.

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) Using the notation in section 9.6 of our text, which of the following choices would be the proper way to indicate that the initial speed of the 'hitter' particle, as observed in the LAB frame, is equal to the final speed of the 'hittee' particle, as observed in the CM frame?

  1. u1=u2'
  2. u2=v1'
  3. v2=u1'
  4. u1=v2'

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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