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Oh, aG is the acceleration of the center of mass. And yes I understand how to calculate moments and torque, it's just summing the moments about a point other than the center of mass or the rotational axis when considering an accelerating rigid body that I am confused about.

Why are kinetic moments not included in the regular summation of the moments? In other words why is the equation ∑M = ∑Mk and not ∑M + ∑Mk = 0 ? I guess it would help if someone could explain exactly what a kinetic moment is, and why it is equal to the summation of the moments due to external...

So you're saying the book made a mistake? This whole chapter is about how when a rigid body is accelerating, you have to account for the kinetic moments which are the moments of maG about whatever point you're summing the moments about + Iα Here is the diagram containing the kinetic forces that...

In the example they never summed the moments of the applied forces about the centers of mass though? The values they use for the kinetic moments are m1aG1rB and m2aG2rB

Take a look at this example. http://imgur.com/a/Gfxq5 and the solution http://imgur.com/a/8B7Rq And are you sure about being able to apply the parallel axis theorem to that equation? You would get ∑Mp = (I + md2)α; that just doesn't seem right to me. Edit: Oh and I just realized that Iα is...

This is only true if the net torque is calculated about the center of mass on a rigid body. If you are calculating the moment of an accelerating rigid body about a point other than the center of mass, you have to include the moment that maG (where G is the center of mass) makes about that...

Why don't we include the kinetic moments in the summation of the moments of a rigid body? In other words, why are the kinetic moments on the opposite side of the equation as the moments due to external forces? I understand that the math works out but it's not making sense to me conceptually...

I just found that applying an axial load of magnitude σ on both sides of a ductile rod will produce a max in plane shear stress of magnitude σ/2. Why is this? How can there be shear stress if only a normal force is applied?

How about for this problem? Cartons having a mass of 5kg are required to move along the assembly line at a constant speed of 8 m/s. Determine the smallest radius of curvature for the conveyor so the cartons do not slop. The coefficients of static and kinetic friction between a carton and the...

So how do you determine the direction of static friction?

For a particle undergoing a constant velocity circular motion. I thought friction always acted in the direction of motion which would be in the tangential direction.

Hey thanks for the reply, it's good to hear from someone that majored in EP. Did you end up going to grad school for physics? Was it easy to get into a physics grad program? And I posted a picture of the curriculum, could you tell me what you think of it?

I'm not sure if I want to go to grad school for physics or get an engineering job, so I'm wondering if this degree will allow me to do both, so I can pick later on down the road.

I have been stuck between physics and engineering for a while. Someone recommended that I major in engineering physics, as the school I want to transfer to has like the 4th best EP program in the US. I pretty much take all of the physics classes physics majors need (except for labs and...

Thank you for your help though. Hopefully I don't get too many points taken off that quiz.

I don't even think it's possible assuming that the total acceleration is 0.6. You end up not knowing either the tangential acceleration, velocity, or the time.

Damn you're right. I think the problem really just wasn't clear. This was a quiz problem, and what I assumed was that the car decreased in acceleration, and by the time it got to point B, it was at a constant speed of 5.6m/s or something like that. That was the only thing I could come up with...

They didn't state that though? And I asked my professor and he said that the acceleration is 0.6 for the entire motion. Why even give the acceleration at A, after giving the tangential acceleration at A

Because if the overall acceleration is 0.6, and the tangential acceleration is 0.6, then there has to be no normal component, which isn't possible I would have understood if the problem didn't say that the overall acceleration was 0.6m/s^2, and if it said that the tangential acceleration was...

But then there'd be no normal component of acceleration

Sorry, I meant s_ab = 200 + 2pi(50)/4 =278.5m.

s_ab = 200+pi*50/4 = 239.27 m

the tangential acceleration has to decrease because there needs to be a normal component but if you use 15.49^2/50 to find normal accel, that gives you 4.79 m/s^2 which is bigger than the total acceleration

I didn't get the speed at point B. I didn't know how to get there. I got the speed at s=200 which was v=sqrt (2*a*s) = 15.49m/s

Homework Statement A car starts at rest at point A, with a tangential component of acceleration a_t = 0.6m/s^2. Students approximate the acceleration of the car to be 0.6 m/s^2. What are the normal and tangential components of it's speed and acceleration at point B? NOTE : the ends are...

Homework Statement How do you find the derivative of the radial vector r Homework Equations r [/B]= ru'_r + ru_r r = \frac{dr}{dt}u_r + r\frac{du_r}{dt} can't get latex to work either The Attempt at a Solution [/B] If r is the magnitude of r, how would you find the derivative of it...

I've taken a class in C++ and we used Bjarne Stroustrup's Programming: Principles and Practice Using C++. We only got to the point to where we were just starting to learn about pointers, so I still consider myself a beginner. C++ is my first programming language. I really like how Bjarne...

I was actually thinking about doing ChemE a while back. I'm really not sure if I'm interested in the kind of stuff you would be working on as a ChemE though. I did check out that text and it looks interesting. Thank you though! I was actually considering electrical engineering, and I think...

So I am currently a very indecisive mechanical engineering student, who can't figure out what to major in. I have found out that I am much more interested in solving problems that deal with a lot of equations, substitution, and differential equations than I am solving statics problems. I like...

So I was talking to one of my friends who is a huge programmer, and he said that you don't even need a computer science degree to work in software. He said that companies would rather teach a mechanical engineer how to program, than a computer science grad how to problem solve, and that out of...

Ahhh that's true. This seems like the only difference though.

They both study topics in physics is what I mean.

This is true, but how does that change the kind of problem solving skills you would gain? It seems to me that they would be the same as long as an engineering student doesn't skip learning the theory and relate everything to the basics.

How are the problem solving skills you gain from majoring in Physics and majoring in Engineering different? I have noticed that a lot of people think you get better at problem solving by majoring in Physics when compared to engineering, and I don't understand why. I mean, they both study the...

I always hear that mechanical engineers (at least ones without a ton of experience) rarely ever do any math. I really enjoy studying mechanical engineering right now, and I really want to make sure that the stuff I'm studying is what I'll be using on the job. How does a mechanical engineer (or...

I'm not sure if this is the right section but.. During the semester it feels like we are learning a ton of stuff at a crazy pace, but then when the semester is over I always look back and am like "that's it? I've learned everything about X class that I will need to know for all of my future...

I am going to be getting my A.S. in Mechanical Engineering by the end of next semester; however, I am not sure if I should pursue a B.S. in ME or EE. Both degrees would take me 3 years to finish (ME will be 12 credits a semester and one part time semester, EE will be 13-15 a semester. I can't...

I'm trying to figure out why my back hurts when I sleep and I can't figure out the physics behind it. So I sleep on an air mattress. The mattress fits firmly into the frame, which puts a constraint on the mattress to where it cannot expand on it's sides. Think of the mattress as being in a box...

Homework Statement F(s) = \frac{s^2e^{-4s}}{s^2+9} Homework Equations \mathcal{L} ({f(t-a)\mathcal{H}(t-a)}) = e^{-as}F(s) The Attempt at a Solution F(s) = e^{-4s}(\frac{s^2}{s^2+9}) using \mathcal{L} {f(t-a)\mathcal{H}(t-a)} = e^{-as}F(s) f(t) = cos(3t-12)\mathcal{H}(t-4) I do...

That was very well written. And you are definitely correct, although I'm not sure which side that make me lean towards. With physics I would be able to spend my time studying what I love, whereas with engineering I would be able to spend my time doing a job that I enjoy, while also being able to...

You seem to be the one that doesn't have a clue. You think you can determine my knowledge of a topic by reading a short post I wrote on an internet forum. And as I said, I understand that there are things in the middle, but I have considered those things and they do not interest me as much as...

Zapperz, I am choosing between theoretical physics and mechanical engineering because those are the two things that interest me the most. Sure, there are some things in the middle that interest me, but theoretical physics and engineering interest me more. I'd rather just do one or the other

I have been struggling to make this decision for the past year. I am a straight A 2nd/3rd year mechanical engineering student and I really can't decide between engineering and physics. My whole life I have always wondered about the universe, and why things work the way they do. I am way more...

Statics and dynamics textbook?

Thermodynamics (Yunus Cengel Michael Boles , 8) I'm taking Thermodynamics right now at my community college and if you saw my last post about my physics teacher, you know I have the right to be paranoid about not learning enough in my classes. I've always heard Thermo for mechanical engineers...

You're definitely right. I knew that my teacher was skipping a lot of material when I was in the class, but I always thought I was going to major in engineering so I never really worried about it. I did read the whole textbook and learned a lot of extra material, but I didn't really focus on...

I have not taken fluid mechanics yet, the only other engineering classes I have left to take in my AS are dynamics and strength of materials. That is a good idea, I just emailed one of the professors to see what textbook they currently use. It's still kind of discouraging though, I already...

My textbook was Physics for Scientists and Engineers by Serway and Jewett, but I'm not even sure if my teacher followed it she kinda just taught what she wanted to. And my AS is in Mech Eng and I have taken math up to Diff Eq, so my physics classes were calculus based. And I understand that...

I go to a community college for mechanical engineering and I always thought that physics 1 and 2 were way too easy and that my teacher probably skipped a lot of important material. One of my friends just transferred to a university to major in physics and he's been telling me that we didn't...

Would it be a better idea than just taking more ME classes? I can learn how to program on my own but I'm not sure if I'll ever teach myself any of the pure CS classes which is why I thought minoring in it might be a good idea.