# Dynamics: Absolute and Relative Acceleration in Plane Motion

• Drew Davison
In summary: The normal component of acceleration is used to find the acceleration at G and A. Without it, the equation for the acceleration at G and A would not be valid.
Drew Davison

## Homework Statement

A force P is applied to the rod which rests on a horizontal table. The following accelerations are produced. aA= 3.6m/s2 to the right, α of the rod = 6 rad/s2 CCW. Determine the acceleration of point G and B

## Homework Equations

aG=aA+aG/A
aG=aA+[(aG/A)tangential + (aG/Anormal)]
aG=aA+[(α X rG/A) + ( ω2 * rG/A)]

## The Attempt at a Solution

So I tried to solve the problem and quickly found that there is no way to solve for angular acceleration (ω). Looking at the solution they completely leave out the normal component of acceleration to solve for the acceleration at G and A. They just plug in values for acceleration at A, angular acceleration and distance from A to G.

I can't figure out why there is no normal component of acceleration in this problem.
Any help?
Thanks!

is there a force parallel to AG?

No only the forces that are show. The evaluation of the question only involves the accelerations

Drew Davison said:

## Homework Statement

A force P is applied to the rod which rests on a horizontal table. The following accelerations are produced. aA= 3.6m/s2 to the right, α of the rod = 6 rad/s2 CCW. Determine the acceleration of point G and B

## Homework Equations

aG=aA+aG/A
aG=aA+[(aG/A)tangential + (aG/Anormal)]
aG=aA+[(α X rG/A) + ( ω2 * rG/A)]

## The Attempt at a Solution

So I tried to solve the problem and quickly found that there is no way to solve for angular acceleration (ω). Looking at the solution they completely leave out the normal component of acceleration to solve for the acceleration at G and A. They just plug in values for acceleration at A, angular acceleration and distance from A to G.

I can't figure out why there is no normal component of acceleration in this problem.
Any help?
Thanks!
Do you know how to work with the center of mass ?

Drew Davison said:
No only the forces that are show. The evaluation of the question only involves the accelerations
Then why should there be an acceleration in that direction?

## 1. What is the difference between absolute and relative acceleration?

Absolute acceleration refers to the change in velocity of an object without considering any external reference frame, while relative acceleration takes into account the change in velocity relative to another object or reference frame.

## 2. How is acceleration calculated in plane motion?

In plane motion, acceleration is calculated using the formula a = dv/dt, where a is the acceleration, v is the velocity, and t is the time. This formula applies to both absolute and relative acceleration.

## 3. What is the significance of acceleration in plane motion?

Acceleration is a crucial concept in plane motion as it helps us understand how the velocity of an object changes over time. It also allows us to predict the future motion of an object based on its current acceleration.

## 4. Can an object have both absolute and relative acceleration?

Yes, an object can have both absolute and relative acceleration. For example, a car moving at a constant speed on a straight road may have zero absolute acceleration, but if it turns, it will have a non-zero relative acceleration as its velocity changes with respect to the reference frame of the road.

## 5. How does the direction of acceleration affect an object in plane motion?

The direction of acceleration can affect an object in plane motion in several ways. If the acceleration is in the same direction as the velocity, the object will speed up. If the acceleration is in the opposite direction, the object will slow down. And if the acceleration is perpendicular to the velocity, the object will change direction without changing speed.

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