# Understanding solution method for finding accelerations in a mechanical linkage

## Homework Statement

I was checking my work and Chegg uses the equations differently. Can somebody tell me why? Maybe I'm misunderstanding how/why to use the equation I chose.

## Homework Equations

They say aB = -ω2ABRB/Ai
I used aB = aA + αk x r - ω2rB/A

## The Attempt at a Solution

So obviously mine will be a different answer, I only found aB but it gave me an i and j component because of that cross product. Which one is correct and why? Why can they neglect the cross product?

TSny
Homework Helper
Gold Member
The cross product term involves angular acceleration of the rod connecting A and B. In the Chegg problem, the angular acceleration is apparently zero.

How do they justify there being no angular acceleration? It doesn't say this is a static situation, so these bars should be rotating towards one another.

How do they justify there being no angular acceleration? It doesn't say this is a static situation, so these bars should be rotating towards one another.

I figured it out. The problem states that the velocities are constant and therefore the angular accelerations are zero.
Man, reading is important. Thank you for explaining this to me!