Thompson+M;+Week+3

__ **-** __ __ **Week 07 ( 05th of March, 2012)** __
 * There is something else that I forgot to comment on ..... thank you for your honesty. I enjoyed reading your week 3 write-up ! - professor**

01 . An object is hung from a spring balance attached to the celing of an elevator cab. The balance reads 65 N, when the cab is standing still. What is the reading when the cab is moving upward,

(a) with a constant speed of 8 m/s and

(b) with a speed 8 m/s while decelerating at a rate of 2.4 m/s²

note* keep in mind that the spring- balance is measuring tension

(a) First write down the formula ( mg-T=ma ), which is T = ma + mg, with acceleration being zero, then the formular now becomes T = MG.\ So the balance still read the same Force (Tension)

(b) Because it is decelarating a= -2.4 m/s^2 T = mg + ma---> (1) and in order to find mass we use the formula T = mg (65N = M(9.8) --->(2) now that we have the mass we can substitute it in equation 1 to get (T = mass(9.8) + mass (-2.4))-> (3) so we solve equation 3 to get the tension **Professor's comment**: very good Thompson. Good work and keep up !  (there you go my first comment !! a good one too !)

A pelican flying along a horizontal path drops a fish from a height of 5.4 m. The fish travels 8.0 m horizontally before it hits the water below. The acceleration of gravity is 9.81 m/s2. a) What was the pelican’s initial speed? b) If the pelican was traveling at the same speed but was only 2.7 m above the water, how far would the fish travel horizontally before hitting the water below

1) Given: (y-yo), a and Voy using the equation (y-yo) = (Voy)t + 1/2t^2, we can find the time now that we have the time we can now use the equation (x-xo) = (Vox)t+1/2at^2 to find (Vox) We can find Vo by using, Pythagorean theorem equation Vo = sqrt((Vox^2)+(Voy^2))

2) Given: (y-yo), Voy,, a, Vox first we have to use the equation (y-yo) = (Voy)t + 1/2at^2 to find the time

so we can now use the equation; (x-xo) = (Vox)t+1/2at^2 to find (x-xo) :)

Week Four (13 th February, __2012__)

A 0.5 kg rock is projected from the edge of the top of a building with an initial velocity of 10.5 m/s at an angle 54º above the horizontal. Due to gravity, the rock strikes the ground at a horizontal distance of 15.3 m from the base of the building. Assume: The ground is level and that the side of the building is vertical. The acceleration of gravity is 9.8 m/s². What is the height of the building?


 * 1) I usually draw a visual with all the component given in order to get a better picture of what is happening
 * 2) I __list__ what is given and what is missing (Given: Vi, Angle, Ax, Ay, (X-Xo), Missing: Vox, Voy, Δy(building height), time.
 * 3) So first i find the Vox and the Voy using the formulas: Vox - Vo*Cos  θ and Voy=Vo*Sin θ
 * 4) We can also use  Δx = Vox(t)+(1/2)Ax(t^2) to find the time (this equations is converted to Δx=Vox(t), since the (1/2)a(t^2) cancels out because the Vox is 0.
 * 5) Δy(Building Height) = Voy(t)+(1/2)Ay(t^2). Using this equation will give us the height of the building. (Note: Ay(vertical component of the acceleration) = gravity)
 * 6) We substitute the number into the equation and voilà !!

So at first i didn't quite understand what i was supposed to do or even how to approach this problem. And so I went around reading how everyone else explained it. Some examples where more clearer than other so I had to go through a few of them to completely understand. I am not sure if that was __cheating__ but to me it was a __learning__ process. So __thank you__ everyone!

__ **Week three (06th of February,** __**2012__)__** 1. If ** B ** is added to ** A ** the result is 6.0 iˆ + 1.0 jˆ. If ** B ** is subtracted from ** A **, the __result__ is - 4.0 iˆ + 7.0 jˆ.

i. __**Find**__ __**A and B**__
 * The first __step__ is to combine ( **B** + **A** ) and ( **A** - **B** )
 * Doing this will allow us to set up an equation so we can solve for either **A** or **B** (in this problem its easier to solve for (** A **)
 * Example equation: ( **B** + **A) +** ( **A** - **B)** **= (6.0i^+1.0j^) + (-4.0i+7.0i^)**
 * After solving for one variable (In my case; " **A** "), you have to plug it back into the original equation (made from the above __step__), in order to find the second variable (in my case; " **B** ")

ii. __**Find the magnitudes of**__ __**A and B**__
 * To find the magnitude we can use the //Pythagorean Theorem//
 * Magnitude = Sqrt[** A **2 + ** B **2]

iii. __**What is the angle between**__ __** A and B **__ >>
 * The angle between **A** and **B** can easily be calculated using the formula below
 * **A **x **B **=| **A ** |x | **B **| x ** cos(theta) **