Relative Motion Analysis: Acceleration

In summary, the conversation discusses the use of sine and cosine values in rigid body relative motion problems using vector analysis. It is important to use whichever trig functions are needed to solve the problem, rather than just relying on sine and cosine. An example is provided where the velocity components of B are needed, and the speed and direction of motion can be used to find these components. This conversation was moved to the homework forum for further discussion.
  • #1
Smoker
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Mentor note: moved to homework forum later, therefore no template.

When doing a rigid body relative motion (accel) problem using vector analysis, how do I know when it's appropriate to substitute sin/cos values vs when to use just the numbers given as the velocity?
 
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  • #2
It sounds like you are trying to use formulas without understanding them.
vis: sine and cosine are usually used to compute components of vectors resolved against a coordinate system, or against other vectors ... so that is when you use them. You should use whichever trig functions you need to in order to work the problem, not just sine and cosine.

The trouble with this sort of question is that the people who can answer you find this stuff intuitively obvious - this means there is a bit more information needed to get us (me) to understand where the trouble lies.

Please provide an example of where you get in trouble deciding what to use.
 
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  • #3
Post moved from the technical forums, so no HH Template is shown
I am to determine the velocity of slider block C. Given angular velocity of AB (4.1) and angular rotation of AB (5.5).
Screen Shot 2016-03-03 at 5.01.46 PM.png
 
  • #4
Okay, and which velocity value where do you want to calculate how, where you ran into the problem of post 1?
 
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  • #5
mfb said:
Okay, and which velocity value where do you want to calculate how, where you ran into the problem of post 1?
Basically I want to know the x and y components of the velocity of B, A is zero because it's fixed and C is (Vc)i because it's restricted to the x axis, but what is Vb? and why?
 
  • #6
Okay. Can you find the speed of B, and the direction of motion?
That allows to find the velocity components.

I think this thread fits better to the homework section.
 
  • #7
Just a note re initial question about when to use sine and cosine:
If the speed of C is ##v_c## then the x-component is ##v_{cx}=v_c\cos\theta## but, here, ##\theta = 180^\circ## (it is the angle ##\vec v_c## makes to the +x-axis). So you get ##\vec v_c = -v_c\hat\imath## ... which is to say, the sine and cosine values are still used, it's just that they are easy.
 

Related to Relative Motion Analysis: Acceleration

What is relative motion analysis?

Relative motion analysis is a method used to analyze the motion of objects in relation to one another. It takes into account the motion of a frame of reference and how it affects the motion of other objects within that frame.

How is relative motion different from absolute motion?

Absolute motion is the measurement of an object's motion in relation to a fixed point, while relative motion is the measurement of an object's motion in relation to another moving object or frame of reference.

What is acceleration in relative motion analysis?

Acceleration in relative motion analysis is a measure of how an object's velocity changes over time in relation to another object or frame of reference. It can be positive, negative, or zero depending on the direction and rate of change of an object's velocity.

What factors can affect an object's acceleration in relative motion analysis?

The acceleration of an object in relative motion analysis can be affected by factors such as the force acting on the object, the mass of the object, and the direction and speed of the object's motion in relation to a frame of reference.

How is relative motion analysis used in real-world applications?

Relative motion analysis is used in a variety of fields, such as engineering, physics, and navigation. It can be used to calculate the motion of vehicles, projectiles, and other moving objects, as well as to design and optimize systems for efficient motion and navigation.

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