Would The Position of the Center of Mass Change Position?

1. Apr 12, 2014

student34

Take a uniform density bar in space for example. Would the center of mass move if the bar was struck at the very tip perpendicularly by some weight?

2. Apr 12, 2014

mafagafo

It depends. If the bar only acquires angular momentum, its center of mass will not move¹². But in any realistic situation, linear momentum will be acquired in this collision and the center of mass will be displaced.

¹] I am assuming the a center of mass is initially at rest.
²] If the bar was not of uniform density, the center of mass could have its position changed even by angular momentum alone.

Note that I am no physics adept.

3. Apr 12, 2014

nasu

Is this a homework problem?
What do you think? Is there a force on the bar during collision? What happens when a force acts on the bar?

4. Apr 12, 2014

student34

I only want to know for sure.

5. Apr 12, 2014

student34

no

I am not sure, but I do know that the further away from the center of mass the force is the less acceleration the center of mass would have. I just have to imagine tapping the center of the bar with my finger and then tapping the end. So it does seem like the acceleration of the center of mass might go to zero when the force is at the very end of the bar. However, I don't know what physics equation proves this.

6. Apr 12, 2014

nasu

You may need to revise what you think you "know".
For example here:
http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/n2ext.html

The acceleration of the center of mass does not depend on the torque of the external force in respect to the center of mass.

7. Apr 13, 2014