Conceptual question - relative accleration of rigid bodies

• prettydumbguy
In summary, according to the student, the problem with the dynamics class example is that it does not obey what they learned in physics classes. There is more than one way to calculate the acceleration of a object, and the acceleration of BD in the example does not match what is expected.
prettydumbguy
To my knowledge, link AB should only have a normal component of acceleration. Whereas, link BD could have a combination of both normal and tangential. Also, point P will only a tangential acceleration.

Even though link AB has constant angular velocity, doesn't mean that BD will also have constant angular velocity. As if you were to do the relative velocity diagram of this problem you'd notice that there is both translation and rotation of link BD.

Sirsh said:
To my knowledge, link AB should only have a normal component of acceleration. Whereas, link BD could have a combination of both normal and tangential. Also, point P will only a tangential acceleration.

Even though link AB has constant angular velocity, doesn't mean that BD will also have constant angular velocity. As if you were to do the relative velocity diagram of this problem you'd notice that there is both translation and rotation of link BD.

Hmm, so if I have theta=0, AB and BD are both going straight up and D is at its highest point, what happens then? The normal acceleration in AB doesn't change, but then the acceleration of BD would be (alpha x rBD) + w x (w x rBD). So the tangential acceleration would be k x j = i. Then the normal would be j x k = i, k x i =j? I think I get it now.

1. What is relative acceleration of rigid bodies?

Relative acceleration of rigid bodies is the rate of change of their relative velocities. It describes how the velocity of one rigid body changes with respect to another rigid body.

2. How is relative acceleration different from absolute acceleration?

Absolute acceleration is the change in velocity of an object with respect to an inertial frame of reference, while relative acceleration is the change in velocity of one object with respect to another object. In other words, absolute acceleration is measured with respect to a fixed point, while relative acceleration is measured between two moving objects.

3. Can the relative acceleration of two rigid bodies be zero?

Yes, the relative acceleration of two rigid bodies can be zero if their velocities are constant or if they are moving in parallel with the same velocity.

4. What factors affect the relative acceleration of rigid bodies?

The relative acceleration of rigid bodies is affected by the masses of the bodies, the distance between them, and the forces acting on them. It also depends on the type of interaction between the bodies, such as friction, tension, or gravity.

5. How is relative acceleration used in real-world applications?

Relative acceleration is used in various fields such as engineering, physics, and biomechanics to analyze the motion of objects and understand how they interact with each other. It is also used in designing machines and structures to ensure their stability and safety.

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