# Homework Help: Clarification on different kinds of acceleration

1. Feb 16, 2015

### henry3369

1. The problem statement, all variables and given/known data
Not a homework question, I just need clarification.
I'm slightly confused on the different kinds of accelerations involved in a rotating body. I often see three types of acceleration:
2. tangential
3. angular

I'm assuming radial acceleration is the same as centripetal acceleration. So is tangential acceleration the same thing as the linear acceleration of the body being observed while angular acceleration is the acceleration of the rotation (which points in the same direction of the axis of rotation I believe)? Also when a question asks: What is the resultant acceleration of the rotating body, what am I solving for?

2. Feb 16, 2015

### Staff: Mentor

Yes, you have it right. The angular acceleration vector lies along the rotation axis and its direction is usually assessed by way of the right hand rule (for right-handed coordinate systems).
This can sometimes be context dependent, but generally it refers to the total acceleration felt by the body. If you were to draw a Free Body Diagram for the body, it would be sum of all the accelerations acting on it.

3. Feb 16, 2015

### henry3369

So is linear acceleration the same as tangential acceleration?

4. Feb 16, 2015

### henry3369

Or is tangential acceleration a component of linear acceleration?

5. Feb 16, 2015

### PhanthomJay

yes
in a direction tangent to the curve
yes[, using right hand rule
for pure rotation, the resultant of the tangential and radial accelerations

6. Feb 16, 2015

### brainpushups

For rotational motion it is convenient to break the vectors into radial and tangential components rather than x and y components (in a plane). If something is forced to rotate around a point with its radius fixed then there is a centripetal acceleration that points inward; this acceleration just serves to change the direction of motion. A tangential acceleration in this case will result in a change in speed.

7. Feb 16, 2015

### PhanthomJay

it is not a component

the term 'linear acceleration' is most often used in reference to translational acceleration of the center of mass along a straight line, but I suppose it's ok to refer to tangential acceleration as linear acceleration of a particle at any point on the curved path, noting that it's direction is always tangent to the curve.