»»For the next four problems, we suggest you work the elastic collisions in the
ID: 1786130 • Letter: #
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»»For the next four problems, we suggest you work the elastic collisions in the centre-of-mass reference frame; see the handout given in class.Your textbook suggests working in a reference frame where one object is stationary (p. 267) but you still need to remember eq. 10.42. In the centre-of- mass frame, the velocities reverse, which is very easy to remember: ifobjects I and 2 have velocities v and v2 in the lab frame, then object 2 has velocity v2-vi with respect to object I, ie. in the reference frame of object 1 An object with a mass of 45.9 g is moving uniformly with a velocity of 38.0 m/s along the positive x-axis. A second object, of mass 334 g, is moving at +5.6 m/s along the same line, in front of the first mass 2. [lpt] Using the usual sign conventions, what is the velocity of the centre-of-mass of the two objects? Correct,computer gets: 2.4e+01 m/s 3.[lpt] What is the velocity of the first particle, in the zero momentum frame, after an elastic collision? Answer: Not yet correct, tries 6/15 4.[1pt] Using your answer from the previous question, determine the velocity in the laboratory frame, of the first particle after an elastic collision. Answer: Not yet correct, tries 1/15 Subm Al Answers AnswersExplanation / Answer
4.
Use eqn,
V1’=[(m1-m2)v1]/(m1+m2) + 2m2v2/(m1+m2)
V1’=[(45.9-33.4)*38.0]/(45.9+33.4)+ (2*33.4*5.6)/(45.9+33.4)
V1’= 10.7 m/s
3.
Velocity of 1st particle relative to the CM = 10.7 – 24.4 = -13.7 m/s
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