Homework Help: New to classical mechanics

How much physics have you taken?

 

You can do it, but its going to be painful .

Have you taken any classes in statics or dynamics?

 

Just work through it and ask questions I guess. How old are you? This book is for seniors/grad students. Its going to assume you know a lot of background material.

 

calculus 1,2,3. Ode's, some linear algebra, and statics and dynamics.

How is your math background?

 

Statics is a course on, statics. :tongue2: You should know this from your mechanics course.

Given your background, I think you could read through the book you have. But it will still be tough unless you have some experience with statics and dynamics.

 

I am going to take a very quick stab at it but it might be wrong.

Draw a free body diagram along the incline with all the forces labeled on the particle. You will have gravity acting down, and it will be the only force. Then find the component in the direction opposing motion. Once you do this, write your equations of motion and solve them given your initial conditions.

I got this as the final answer:

[tex] t= \frac{v_0}{2gsin(\alpha)} [/tex]

Edit: I had the fraction inverted by accident.

Do you know what the answer is?

 

Show some work. What are you doing/getting?

 

For a book of this level, I cant teach you how to write the equations of motion. You have to do that on your own. If you cant, going through this book is going to be hopeless. This book isnt going to hold your hand, so expect things to get a LOT worse than this simple problem.

Write the equations of motion for starters.

Lets be clear, you are reading https://www.amazon.com/Classical-Dynamics-Particles-Systems-Thornton/dp/0534408966 book, yes?

 

Almost, those v_0 are wrong, and you have sign errors.

 

Velocity components have nothing to do with force balance-velocity is not a force.

You need to use a body fixed coordinate system, not an absolute coordinate system. The x-direction should be pointing up the incline, not horizontally and to the right as your thinking.

Also: this is incorrect and written incorrectly as well:

F = ma = -m sin x + m cos y

F is a vector, everything you do in this book will be for a vector from now on.

F=ma=-msinx (i) + 0(j) + m cosy(k) (This is not correct, but the vector notation is).

If you are struggling with this, I would recomend that you read https://www.amazon.com/Engineering-..._bbs_sr_2/103-6206101-2550252?ie=UTF8&s=books book first on statics.

You will learn more about vectors, how to do force balance, moment of inertia etc. Your basics right now are too weak for the book your using.

 

Once you finish the statics book, work through this https://www.amazon.com/Engineering-...=pd_bbs_1/103-6206101-2550252?ie=UTF8&s=books book.

Once you do these two books, read the book you are reading now.

 

I recomend you use those books.

If you need help doing simple force balance, trust me, you are not yet ready to dive into this book.