# ME 203 Homework

## Fall 2014

You wanted me to post about what we discussed after class today...

For question 2, I wanted to know what the forces acting on the system were, as far as the orientation of the normal forces and if there would be any sort of friction or traction forces.

Thanks for the help, hopefully this is a good enough summary question for what we discussed.
How should we go about getting the direction for the ray from origin to B?
The composite vector rB/O can be found by adding the vectors rA/O and rB/A together. Then its direction, which is of unit length, can be determined by simply diving rB/O by its magnitude.
For problem number three on the hw, once you have plotted the position, velocity and acceleration functions using matlab how would you identify the value of time at which the ball hits the ground on the graph at y=0? I don't understand how to interact with the matlab graph when it comes to pulling data from the graph. When I plotted the function on my calculator, I was able to get t=4.106s at y=0.

I would just do the same with MATLAB. Plot the function and then visually find when the graph crossed y = 0.

Just when you thought that it couldn't get any better... Homework 02

Lyric of the day
So I got to keep on walkin'
I got to walk on

Dr. Quinn,

For question 2, after taking the integral twice, we produced the equation 4 = .02e^t. After taking the natural log, we found the final time as 5.3 seconds. This gave us 4 for both velocity and acceleration. This seems incorrect.

Can you please let me know if we made a mistake in our calculations?

Thanks!
Hi. Since the derivative of the exponential function y(t) = et is exactly dy/dt(t) = et, then this result makes sense...

Note however, that the units of the position and velocity are different. Can you find the source of this?

Just like Jack... Homework 03 is back.

Lyric of the day
Well relationships change,
Oh I think it's kinda strange,
How money makes a man grow.

It's hard to come up with a new quip for each homework. Oh well, here's Homework 04

Lyric of the day
I felt a little fear upon my back
He said "Don't look back, just keep on walking."

I think I'm over-thinking the first problem here, but I keep getting tripped up with units. My theta-dot is in rad/s since theta is a function of time. But the position of the particle is given in mm. When I go to find the magnitude, I end up with different units coming from the e_r and e_theta directions. Again, I think I'm just over-thinking it most likely, but I would appreciate some help.
Nevermind, I think it worked itself out in my head after a little while. I do get a fairly large acceleration in mm/s^2 though, so I hope it worked itself out correctly...
This question is for problem 4 (hw#4)

In the question, it states that;

A cameraman standing at A is following the movement of a race car, B, which is traveling along a straight track at a constant speed of
80 ft/s.

In the figure that goes along with this problem, it uses points C and O. Is c the car and therefore point B, why the cameraman is standing at point O? I'm sure this is a silly question but I just wanted to make sure that I had my problem set up the right way.

--Thank you.
Yes, that is the right interpretation. I inadvertently changed the labels when I made the figure...

Homework 08 has been delayed due to weather.

Lyric of the day
Everywhere you go
Always take the weather with you