Question

What reasons do you have to choose a particular mass or avoid it?

a. Use: The center of mass in a free rotation problem.

b. Use: The fixed point in a rotational problem.

c. Use: The point were the largest force is applied.

d. Avoid: The axis of the net force.

e. Avoid: The line of zero angular momentum

Note: There can be more than one answer.

Answer 1

The correct answers for this question are (a),(b) and (e)

Notes-

1- We use centre of mass in free rotation because it is the point where whole mass of the body lies and force acts on this point.

2- We use the fix point in rotational motion because we can apply conservation of angular momentum about that point and solve the problem.

3-This is not necessary to choose a point where the largest force applied.

4- We use the axis of net force to find the direction of net force and corresponding quantities.

5- In rotational problem we are interested in conservation of angular momentum so we need to choose the line which have finite angular momentum.

I hope the above work will help you.
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