Discussion Questions: 11/8/12


1. How are change and continuity a part of science?
Continuity is a part of science because new models and ideas are constantly being proposed and accepted over time, such as the models of the motion of the planets. Change is a part of this science because these models always bring new questions and better understanding to the concept. For example, the Babylonians first had an accepted model for the motion of the planets, as well as the Greeks. Eventually, more scientists like Copernicus and Ptolemy decided to create newer models to explain this motion, which changed the thinking of the way the planets moved.

2. Although Ptolemy's system is no longer the accepted view of the universe, was his system "unscientific" by modern standards of science? Explain.
No, Ptolemy’s system was not really very “unscientific” because of the way he conducted his experiments to create his theory. He first had a hypothesis and then he made observations and mathematical calculations to support it. His mathematical data and observations were what led him to create his theory.

3. Was Copernicus's system an improvement over Ptolemy's? Why?
Copernicus’s system was not much of an improvement over Ptolemy’s system. This is because Copernicus based his work on the Greeks’ work, which was actually very inaccurate, making his own model inaccurate. However, he did work out the mathematics of the heliocentric system of the universe. He did not invent this system, though.

4. In what ways have scientists' preconceptions gotten in the way of science?
Scientists’ preconceptions gotten in the way of science because the public sometimes adopts the wrong scientific theory, slowing down the scientific process. For example, when the public adopted the theory that the sun moved around the earth, people were not willing to accept the correct theory that the earth travelled around the sun. Also, when people adopted the theory that the planets had circular orbits, they were unwilling to accept the theory that they were actually elliptical orbits.

5. A common conception is that scientists work alone and in isolation from other ideas. Do you agree? Why?
I disagree with this conception because scientists always work together and always use each others’ work. This was the case in the past, as well as the present. Scientists today communicate more than ever, especially with the internet. Scientists share their data and observations with others so that they can compare with each other or use them to help each other.

6. How does technology affect progress in science?
Technology has become a huge part of modern science. Science would have been stuck in the 1800s if it were not for some major technological advancements. These advancements really helped science evolve into what it has become not. It has allowed for certain tools to be used by scientists. For example, in modern days, scientists can use internet connection and satellites for many advanced experiments.


1. On Quicktime, each frame is 1/15 of a second, So, the following data was obtained:

Horizontal Distance vs Time of a Marble
Time (seconds)
Horizontal Distance (cm)
5.06667
0
5.13333
18
5.2
30
5.26667
40
5.33333
53
5.4
69
5.46667
88

Using the formula v=∆d/∆t, the velocities were determined:

Horizontal Velocity vs Time of a Marble
Time (seconds)
∆ Horizontal Distance (cm)
Velocity (cm/s)
.0667
18
269.9
.0667
12
179.9
.0667
10
149.9
.0667
13
094.9
.0667
16
239.9
.0667
19
284.9
The following is a graph of the data that is provided on the tables:graph1.png
Since this graph has a somewhat linear trend, I can conclude that the horizontal velocity of the marble is constant. The small dips in the graph are probably just from errors while looking at the video when I was trying to record the position and time of the marble.

2. The following data was obtained from the video:

Vertical Distance vs Time of a Marble
Time (seconds)
Vertical Distance (cm)
5.06667
87
5.13333
83
5.2
77
5.26667
71
5.33333
58
5.4
38
5.46667
5
Using the formula v=∆d/∆t, the velocities were determined:

Vertical Velocity vs Time of a Marble
Time (seconds)
∆ vertical Distance (cm)
Velocity (cm/s)
.0667
-4
-60
.0667
-6
-90
.0667
-6
-90
.0667
-13
-194.9
.0667
-20
-299.9
.0667
-33
-494.8
This table clearly shows that the velocity is not constant. As time goes on, the marble clearly increases in speed in the negative direction. It goes from -60 cm/s to -494.8 cm/s in the time that it took to fall to the ground. The acceleration of this fall should be close to 9.8 m/s^2.

Unit 12: Magnetism

4/22/13


Concept Outline:


  • The right hand rule for a current-carrying wire can be used like this:

external image right-hand-rule.jpg
  • Fingers point in the direction of the magnetic field and thumb points in the direction of the current.
  • The other right hand rule can be used to determine the direction of the force on a particle, given the velocity and magnetic field directions: thumb points in the direction of the force; fingers first point in the direction of the velocity, and then waive to the direction of the magnetic field.
  • The first right hand rule can be used to determine the direction of the magnetic field on a solenoid:
external image img16.jpeg

  • Useful formulas:
    • F=qvb(sin(θ))
    • F=ILb(sin(θ))
    • For straight wire: B=(UI)/(r2pi)
    • For loop of wire: B=(NUI)/(2R)
    • For solenoid: B=(UIN)/L
    • U=mu knot=4pi * 10^(-7)

Multiple Choice Questions


1) What is the direction of the force of this electron?
001 (4).jpg
a) up
b) down
c) left
d) right
e) into the page

2) A long straight wire has a current of 2 Amps. What is the strength of the magnetic field .2 meters from the wire?
a) U/(.2pi)
b) U/pi
c) 0
d) .8
e) .2468

3) A loop of wire has a .5 m radius and 200 loops. If the current is 10 Amps, determine the magnitude of the magnetic field in the center.
a)1U
b)U
c)100U
d)1000U
e)0

4) A solenoid that is 20 meters long has 200 turns of wire and a 1 Amp current. What is the magnitude of the magnetic field?
a)2
b)0
c)100U
d)10U
e)20U

5) A solenoid has a B-field of 5 Teslas. It has a resistance of 2 ohms. It has 400 turns. It is 1 meter long. Find the potential difference.
a)1
b)40U
c)1/40U
d)4.567889
e)40
f)This answer is wrong

Open ended question
A loop of wire, as shown in the figure below, is suspended in air magnetically.

001 (5).jpg

a) Determine the magnitude and direction of the current in the wire if it has a mass of 3 kg.
b) Determine the magnitude and direction of the current in the wire if it has a mass of 5 kg.
c) Determine the magnitude and direction of the current in the wire if the right/left sides of the wire were 7 meters.
d) Determine the magnitude and direction of the current in the wire if the right/left sides of the wire were 20 meters.
e) what did you notice about the answers in c and d? Explain.


Lab
Obtain a solenoid, amp meter, resistor, and compass. Hook up a power supply to the solenoid and place the compass around the solenoid and inside of it. Record what the compass does at different locations around and in the solenoid. Adjust the current that is going through the solenoid using a variable resistor. Analyze the data and observations that were recorded in the experiment.