# Multiple choice ? on center of mass

• srhly
In summary, when transforming from the lab frame to the center-of-mass frame, the velocities of m1 and m2 will be v1com=+v1-Vcom and v2com=+v2-Vcom, respectively.~~
srhly
Two balls of masses m1 and m2 are moving along x-axis w/ velocities, v1>v2>0. After transforming from the lab frame to the center-of-mass frame, what are the velocities of m1, v1com, and mass m2, v2com? Vcom is the center of mass velocity for the system of both balls. The choices are:

1.v1com=+v1-Vcom, v2com=+v2+Vcom
2.v1com=+v1-Vcom, v2com=+v2-Vcom
3.v1com=+v1+Vcom, v2com=+v2+Vcom
4.v1com=+Vcom, v2com=+Vcom
5.v1com=+Vcom-v1, v2com=+Vcom+v2
6.v1com=+v1+Vcom, v2com=+v2-Vcom
7.v1com=+Vcom+v1, v2com=+Vcom-v2
7.v1com=+Vcom-v1, v2com=+Vcom-v2
9.v1com=+v2, v2com=+v1

srhly said:
Two balls of masses m1 and m2 are moving along x-axis w/ velocities, v1>v2>0. After transforming from the lab frame to the center-of-mass frame, what are the velocities of m1, v1com, and mass m2, v2com? Vcom is the center of mass velocity for the system of both balls. The choices are:

1.v1com=+v1-Vcom, v2com=+v2+Vcom
2.v1com=+v1-Vcom, v2com=+v2-Vcom
3.v1com=+v1+Vcom, v2com=+v2+Vcom
4.v1com=+Vcom, v2com=+Vcom
5.v1com=+Vcom-v1, v2com=+Vcom+v2
6.v1com=+v1+Vcom, v2com=+v2-Vcom
7.v1com=+Vcom+v1, v2com=+Vcom-v2
7.v1com=+Vcom-v1, v2com=+Vcom-v2
9.v1com=+v2, v2com=+v1
Choice #2
(When transforming to COM Frame, the new apparent entity velocities will be relative to Vcom, that is, Vcom will appear subtracted from v1 & v2.)

~~

The correct answer is 6. v1com=+v1+Vcom, v2com=+v2-Vcom. This is because in the center-of-mass frame, the total momentum of the system is zero. This means that the velocities in the center-of-mass frame must be equal and opposite for the two balls, with the more massive ball moving slower and the less massive ball moving faster. Therefore, v1com=+v1+Vcom and v2com=+v2-Vcom.

## 1. What is the center of mass in a multiple choice question?

The center of mass in a multiple choice question refers to the point at which the distribution of mass is balanced. In other words, it is the point at which the question is equally likely to be answered correctly or incorrectly by a group of individuals.

## 2. How is the center of mass determined in a multiple choice question?

The center of mass in a multiple choice question can be determined by analyzing the data from a group of individuals who have taken the test. This can be done by calculating the average number of correct responses for each question and identifying the point at which the average falls.

## 3. Why is the center of mass important in multiple choice questions?

The center of mass is important in multiple choice questions because it can help identify the difficulty level of a question. Questions with a center of mass that falls towards the correct answer are considered easier, while questions with a center of mass that falls towards the incorrect answer are considered more difficult.

## 4. Can the center of mass change in a multiple choice question?

Yes, the center of mass can change in a multiple choice question. This can happen if the test is taken by a different group of individuals, or if the test is revised to include different answer choices.

## 5. How can the center of mass be used to improve multiple choice questions?

The center of mass can be used to improve multiple choice questions by identifying questions that are too easy or too difficult. This information can then be used to revise the question or adjust the difficulty level of the test. It can also be used to compare the performance of different groups of individuals taking the test.

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