Finding the Center of Mass for Stacked Cubes of Different Masses

[PeachBanana]

Homework Statement

9) Three cubic boxes, each with side 0.1m, are stacked on top of one another. The lowest one is filled with gold bars and has mass 25kg; the middle one contains aluminum bars and has mass 10kg. The top one contains balsa wood and has mass 2kg. The height above the floor of the center of mass of the three boxes is _______.

Homework Equations

$\Sigma$mx / $\Sigma$m

The Attempt at a Solution

I put the origin at the bottom of the gold bar.

(25 kg)(0.1m) + (10 kg)(0.2 m) + (2 kg)(0.3 m) / 37 kg = 0.137 m

 

[tiny-tim]

Hi PeachBanana!

I put the origin at the bottom of the gold bar.

(25 kg)(0.1m) + (10 kg)(0.2 m) + (2 kg)(0.3 m) / 37 kg = 0.137 m

Are these those special boxes with the centre of mass at the top?

 

[PeachBanana]

Oh. It looks like I forgot the rule about symmetrical objects having their CM's in the center.