- #1
mbigras
- 61
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I'm looking at example 16.3 and 16.4 in Beer and Johnson vector mechanics dynamics. It seems that you can draw the forces in your FBD as "effective forces" on your KD (kinetic diagram). I'm confused about how I should choose to draw the effective forces at the centroid G or to draw them where they are acting. In example 16.3 the forces are drawn where they are acting, but in 16.4 they are drawn at the centroid.
One hypothesis that I have is: if the body is in fixed axis rotation then draw the effective forces where they are acting but if the body is in general plane motion then draw the effective forces at the centroid.
Also I'm very interested to hear some helpful ways that you imagine going between drawing forces on a FBD and drawing the effective forces on the KD. I'm taking engineering classes as a physics major and this is my first exposure to effective forces and I'm having trouble understanding where the [itex]\bar{I}\vec{\alpha}[/itex] and the different effective force terms come from.
One hypothesis that I have is: if the body is in fixed axis rotation then draw the effective forces where they are acting but if the body is in general plane motion then draw the effective forces at the centroid.
Also I'm very interested to hear some helpful ways that you imagine going between drawing forces on a FBD and drawing the effective forces on the KD. I'm taking engineering classes as a physics major and this is my first exposure to effective forces and I'm having trouble understanding where the [itex]\bar{I}\vec{\alpha}[/itex] and the different effective force terms come from.