Answer to Question #163034 in Physics for John

Question

Is the centroid and the center of mass 

(COM) of the bird at the same point? Why do you think so. Explain your 

answer.

2. Create a sample problem (looks like in What’s More Section) 

that relates center of mass, linear momentum and net force. Show your full 

solution and answer. You can use at least 3 particles on a system, it may 

be particles due to explosion etc.

Answer 1

The centroid and the center of mass (COM) of the bird are at the different points because the centroid is a geometrical point equally distant from the external points of an object. It does not take into account mass distribution, only shape. COM, on the other hand, takes into account both shape and mass distribution.

Problem: what will be the momentum of COM of a particle with mass M that goes falls at constant velocity v and explodes into three particles? What does the initial motion tell you about the net force?

Solution: according to momentum conservation, the linear momentum after the explosion will be the same as Mv. Since the initial motion was uniform, the net force was zero according to Newton's first law.