Cart on a Ramp!

We did not go over the previous lesson because yesterday was pretty much a weekend and today was something new to work on. Today, we spent about half of the hour going over the blog posting and I was designated to be the first poster. After that we received a lab to work on involving a cart and a ramp.

• We looked at the distance, velocity, and acceleration of the cart moving up the ramp given a small push. 
• The preliminary questions were answered and gave our predictions on what we thought the graphs would turn out like, most groups also had their graphs printed off. 
• Procedure Part I was finished. 
• With this experiment we will figure out the position-time, velocity-time, and acceleration-time graphs which fits with our unit of kinematics. 
• We will also be able to see if the cart maintains a constant acceleration. 

Tomorrow looks to be more promising in content as today was mostly collecting data to analyze.

How to Post

This is so much fun! I love blogging.

Kirchoff's Laws

We started off class by reviewing Kirchoff's Current Law and Voltage Law in series and parallel circuits.

Kirchoff's Current Law

• The current is conserved in a series circuit. It is the same throughout the circuit. I1=I2=I3=IT.


• The total current in a parallel circuit is the sum of the current through each resistor connected in parallel. I1+I2+I3=IT

Kirchoffs Voltage Law

• In a series circuit, th total (Vt) is the sum of the potential difference across each individual resistor connected in series. V1+V2+V3=VT


• In a parallel circuit, the voltage is conserved. The potential drop across each resistor in a parallel is equal to the total voltage. V1=V2=V3=VT

Then we did book questions Page 646#1-4

After that we looked at Electrical Rsistance. Electrical resistance is the amount of current drawn from an electrical energy source depends on the internal resistance of the appliance that is "plugged in" and where R=P(L/A)

R=resistance

P=resistivity

L=length

A=cross-sectional Area

We also looked over Ohm's Law V=IR

• If the voltage is constant , an increase in curent(I) must be the result of a decrease of resistance


• If the resistance is constant, an increase in voltage results in a directly proportional increase in current.

Resistors in Series

The total restistance is equal to the sum of individual resistor on series

Rs=R1+R2+R3+..+Rn

Resistors in Parallel

The total resistance is a reciprocal relatonship.

1/Rp=1/R1+1/R2+...+1/Rn

As more resistors are added, the total resistance becomes less. Therefore, the total current will increase

Current and Electric Potential Energy

We started off the class with current. Current is the flow of charges through a wire similar to water flowing through a hose.



There are two different conventions for current:



1) Coventional Current- electric current originates from the positive terminal and goes to the negative terminal. This is a flow of positive charges.



2) Electron Flow Current- current goes from the negative to the positive terminal and represents a flow of electrons.



The Formula for Current is I=Q/t I=current(amps) Q=charge(coulombs) t=time(seconds)



There are two types of current that exist. The AC or alternating current is when the charges in the current change direction. The DC or direct current is when all the charges in the current travel in one direction.



Ex:Calculate the amount of current flowing through an electri toaster if 900C of charge is used to toast 2 slices of break in 1.5 minutes.



Q=900C, t=1.5min.-90.s I=? I=Q/t---> 900C/90.s=10A



Next we talked about Electric Potential Energy. This concept states that if a negative charge were to be placed between a negatively charged plate and a positively charged plate, the negative charge would be attracted to the positively charged plate. Therefore there would be the maximum electric potential energy between the negative charge and the positively charged plate, and no electric potention energy between the negative charge and the negatively charged plate.

The work done per unit of charge is called the electric potential different and it is equivalent to voltage.The formula is: V=W/Q

V=potential difference(volts)W=work(J)Q=charg(C)

Lastly we learned that an electric potential difference must exist in order for current to flow in an electric circuit.

Hooke's Law

Today in physics we reviewed what we did on Friday which was total energy and how the amount of kinetic energy and the amount of potential energy are always equal to the starting total energy.

We then moved on to look a springs, more specifically, Hooke's Law which contains stuff about the spring constant and how far from equilibrium the sping is depressed or stretched.

Ex: A compressed spring that obeys Hooke's law has a potential energy of 18 J. If the spring constant is 400 N/m, find the distance by which the spring is compressed.

Ep = 18 J

k = 400N/m

x = ?

Ep=1/2kx^2

=to find x we manipulate the formula to get the root of 2ep/k

= the root of 36/400

=3/10 or .30m the spring compressed.

We also looked at finding the total energy and the maximum height of an object, in this case, a golf ball.

Ex: Determind the total mechanical enerygy of a 48g golf ball if it has a velocity of 25 m/s when it leaves the club face.

m = .048 kg

vi = 25 m/s

hi = 0 m

et = 1/2mv^2

=1/2(.048)(25^2)

=15J

b) If the golf ball goes in an arc and has a speed of 15 m/s at its maximum height, what will the maximum height be?

h = ?

Et = 15 J

m = .048 kg

v = 15m/s

Et=mgh+1/2mv^2

15J=(.048kg)(9.8m/s^2)(h)+1/2(.048)(15^2)

And to find h we manipulate the formula and eventually get that the height is 20m.

Landon is next.

Roller Coasters!

You will be completing an assignment that uses the Physics of Energy to explain how a roller coaster works.

For Monday I need you to look over the following list of possible websites to use or to select a video that shows a roller coaster in action.  Choose a video or a program to use.
https://docs.google.com/document/d/1Q6nmNhSqJ6Nn-JXg7HFrjm7m_Gdja076XPdRKqFSu3U/edit

If you are using an online game/animation for your roller coaster, on Monday you will be given time on the laptop in the Physics Lab to make a video of your roller coaster in action.

On Tuesday we will go to the computer lab for you to view your video and come up with the explanation that you will present to the class.

On Wednesday, we will present them!

The general idea behind the assignment is:

Create a roller coaster. Use Smart Recorder to record it or save it if you can.

Present your video to the class. Pause the video as you go to explain the physics behind the motion:

Draw on the screen with the SMARTBoard

• key ideas:
• height
• velocity
• kinetic energy
• gravitational potential energy
• gravity
• use given or arbitrary values for the height to explain why the roller coaster works

Potential Energy and the Law of Conservation of Energy

Today in a heated and somewhat violent Physics class, we learned about potential energy and the law of conservation of energy. We started off by finishing the questions on kinetic energy we did the day before on page 290 #1-4

Then we read pages 291 and 292 in the textbook and answered questions about it.

From the reading we learned some new definitions:

Potential Energy- Energy that is stored and capable of being transformed into other types of energy.

Law of Conservation of Energy- Energy is not created or destroyed in any interaction, but is merely transformed from one type of energy into another.

Mr.Banow used the textbook as per usual to show us that when he holds the book above the floor and the book is not moving it has potential energy.

After the reading we moved on to learn about the most common type of potential energy and the one we will use most often in Physics 30 and that is Gravitational Potential Energy.

Gravitational Potential Energy- the energy stored as a result of the vertical position (height) of an object.

The formula to calculate Gravitational Potential Energy is Eg=mgh where:

Eg is Gravitational potential energy (J)

m is mass

g is acceleration due to gravity

h is change in height relative to the reference point

Ex.1

A 25.0kg box is lifted from the floor to a ridiculously large desk that is a whopping 1.87m above the floor.

a) What is the gravitational potential energy relative to the floor?

m=25kg

h=1.87m

g=9.8m/s^2

Eg=?

Eg=mgh

=(25kg)(9.8m/s^2)(1.87m)

=458J

Jeren (soon to be four eyes) Tuchscherererererererererererer is next