# Recent content by influx

1. ### Question about the inertia matrix of a bar

I I was wondering whether anyone could help me out with this?
2. ### Question about the Triple Product

Homework Statement [/B] Homework Equations a⋅(b x a) = 0 The Attempt at a Solution Is my working below correct? In particular, can you apply the rCB to both the first part of the bracket (0.2j) and the second part (w x rCB) individually like that? My second question relates to: Is...
3. ### Question about the inertia matrix of a bar

Ah that makes sense! This question is from an exam paper set by my university's engineering department a few years ago, is there any way to determine that this rod is infinitely thin from the wording of the question? Does the ''uniform slender'' part suggest this? Also, I was wondering why...
4. ### Question about the inertia matrix of a bar

If the moment of inertia relative to the parallel axis is zero, then why is the moment of inertia about axis ZZ (in my data book) not 0? This axis is parallel to the cylinder?
5. ### Question about the inertia matrix of a bar

I understand that but the x'-x' axis in the question is parallel to the bar and not perpendicular? Thanks
6. ### Question about the inertia matrix of a bar

Homework Statement Homework Equations ml2/12 The Attempt at a Solution So according to my databook: The axis x'-x' in the question corresponds to axis ZZ in the databook image above. That means in terms of radius, the moment of inertia about axis x'-x' is mr2/2. So in light of this...
7. ### Vector Multiplication

Homework Statement Homework Equations RAO = b(Sinβj+Cosβk) The Attempt at a Solution [/B] The box in red is ω. However I am unsure of where they got the box in blue from? As mentioned above, RAO = b(Sinβj+Cosβk) so not sure where they got the box in blue from? I know of the vector triple...
8. ### Determining the rank of a matrix

Homework Statement Homework Equations N/A The Attempt at a Solution I know that they got a rank of 2 since there are 2 linearly independent columns but what if we decided to count rows? In that case we would have 4 linearly independent rows which would suggest the rank is 4? How do we...
9. ### Inverse Laplace transform of 1/s

Homework Statement Homework Equations N/A The Attempt at a Solution The left hand side (red box) is the data sheet provided to us in the exam. The right hand side (blue box) is Wolfram Alpha. The data sheet says that the inverse Laplace transform of 1/s is equal to u(t) (i.e. the unit step)...
10. ### Transfer function of a second order system

Homework Statement Homework Equations The Attempt at a Solution I have done question 1.18 and I understand it completely. However, for question 2.5, I do not understand how they got G(s)? Why isn't the G(s) in question 2.5 the same as G(s) at the bottom of question 1.18? I asked my lecturer...
11. ### Response of a 2nd order system

That makes sense. Thanks
12. ### Response of a 2nd order system

Generally we've Y(s) = G(s)U(s) but in this case it's Y(s)=G(s)U(s) + another term. Is there a reason why we don't have the usual Y(s) = G(s)U(s) ?
13. ### Response of a 2nd order system

I understand that but how did this then lead to the conclusion which of the terms is which? Thanks
14. ### Response of a 2nd order system

Homework Statement Homework Equations N/A The Attempt at a Solution I understand how they got the answer and the calculations they did but I have 3 questions about this screenshot. 1) Why the box in red is the transfer function? Is there a way to tell this from the Y(s) = ... expression? 2)...
15. ### Inertia matrix of a homogeneous cylinder

Sorry for the late reply. I am still confused. I just want to know how they (mathematically) got from the left hand side to the right. I don't understand how integrating the left hand side yields the right hand side.