7
Holt Physics Chapter 7: Rotational Motion and the Law of Gravity I. Section 7-1: Measuring Rotational Motion
A. When something spins it undergoes “rotational motion”. When something spins around a single point it is called “circular motion”. B. We measure how fast something spins not in m/s (different points on the object are spinning at different velocities) but by measuring the angle described in a given time period. C. Angles can be measured in radians (rad)

1. The radian is the ratio of the arc length (s) to the radius (r) of a circle

(insert fig. 7-1 here)

2. The radian is a “pure number” with no units (the abbreviation “rad” is always used) 3. Conversions:
360o = 2π rad
360o = 6.28 rad
Θ(rad) = π/180o Θ(deg)
Θ(rad) = .0174533 Θ(deg)

(insert fig. 7-3)

D. Angular displacement describes how much an object has rotated relative to a reference line

(insert fig 7-4)

Angular Displacement

ΔΘ = Δs/r
angular displacement = change in arc length/radius

E. Watch your sign! Θ is considered positive when rotating COUNTERclockwise (when viewed from above). Therefore an angle of ½π rad = -1½π rad F. Angular Speed (ω = “omega”) describes the rate of rotation. Average angular speed is measured in radians per second.

Angular Speed

ωavg = ΔΘ/Δt
average angular speed = angular displacement/time

G. Angular Acceleration (α = “alpha”) occurs when angular speed changes. Remember acceleration? a = velocity/time ??

Angular Acceleration

αavg = ω2 – ω1/t2 – t1 = Δω/Δt

average angular acceleration = change in speed/time

H. “All points on a rotating rigid object have the same angular acceleration and angular speed.” P.250 II. Section 7-2: Tangential and...

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Free Fall
Rachel Shea
Physics 131 Lab, QL
Hasbrouck 210
Sept. 21, 2014
Abstract
This experiment measures the study of motion by observing the force of gravity acting solely upon an object, and also measures reaction time. If an object is in free fall, the only force acting upon it is gravity. The object used in this experiment was a golf ball that provided some acceleration when dropped. A sensor positioned underneath a table recorded the golf ball’s pattern of motion, when dropped. The main objective of performing this experiment is to measure the velocity and position of the ball to eventually find the acceleration of free fall. A computer program called, DataStudio, was used to create a graph of position vs. time and a graph of velocity vs. time. The second part of the experiment involved randomly dropping a ruler and having your partner catch it to determine reaction time.
Questions
1. The parabolic curves open upward instead of downward because of the golf balls movement over time: where it is dropped from, to where it ends up. The ball begins close to the sensor, then drops to the ground, then bounces back up closer to sensor again, therefore the bounces correspond with the bottom curves of the parabola. If the data were collected from the floor then the curve would open downward. But because the sensor graphs the position from the sensor, the curve was upwards.
2.
-4572009207500
The slope of the velocity versus time graph physically...

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Experiment 7: Relative Density
Laboratory Report
Marella Dela Cruz, Janrho Dellosa, Arran Enriquez,
Alyssa Estrella, Zacharie Fuentes
Department of Math and Physics
College of Science, University of Santo Tomas
España, Manila Philippines
Abstract
The experiment was conducted to show the different methods on how to determine an object’s composition through its density and to determine an object’s density by displacement method and the Archimedes Principle. Results show that. The materials used were the spring scale, beaker, 25 pieces of new 25 centavo coins, a bone from a pig’s leg, diet and regular soft drinks, and a pycnometer.
1. Introduction
Density is a physical property of matter. It is the mass per unit volume of a substance. In this experiment, relative density is also used to be able to determine the composition of the substances or objects used. Relative density is the ratio of a density of a substance to that of the density of a given reference material. It is also known as specific gravity. Density is used when making or building objects that are required to float such as ships on water and airplanes in the sky.
Objectives:
1. To determine the density of an object by displacement method
2. To determine the composition of a substance based on its density
3. To determine the density of a substance by Archimedes Principle
2. Theory
Relative Density (R.D.) or also known as Specific gravity (S.G.), is the raito of...

...accident such as car crash, since the momentum changes instantly, the force becomes extremely great. Impulsive force is produced during the collision and it will cause severe damage to the car, and may also injure the passengers in it. 3 The passengers’ momentum can be stopped by objects in the car such as dashboard, side door, or windshield, however, it will cause serious injuries because the force would be very great. To increase the safety of the driver and the passengers, safety devices such as seatbelts, air bags, crumple zones, and etc. are introduced. Safety devices such as seatbelts, air bags, crumple zones and etc are designed to reduce the forces on the body if there is a collision. These safety devices are mostly made based on the physics principle of force and momentum, which is
This relationship says that if momentum is transferred over a longer period of time, the force involved is less. If the force of a collision can be reduced, then the chances that someone would get hurt in an accident are lower.4 Since momentum cannot be transformed to another form of energy, it is always conserved during any collision. The change in momentum is then a fixed quantity, and to lower the force, changes have to be made in the time of the collision.5 The time required for the car to stop in a collision have to be increased so that the forces that will impact the occupant will be lower, and they will be less likely to be hurt. If the time taken for the change...

...AP Physics Summer Assignment with
Dr. Crymes
Welcome to AP Physics B! It is a college level
physics course that is fun, interesting, and challenging
on a level you’ve not yet experienced. This assignment
will review all of the prerequisite knowledge expected of
you. There are 7 parts to this assignment. By taking the
time to review and understand all parts of this
assignment, you will help yourself acclimate to the rigor
and pacing of AP Physics. The summer assignment will
be “due” the first day of class. Good luck!
1. First off: send me your email address to jonathan_crymes@gwinnett.k12.ga.us so that I can make a class
list and hopefully send you some cool stuff over the summer. No extra work, I promise. Preferably
today, but no later than June 30, email me to introduce yourself. Please include the following
information with your email:
- First name, last name, last math class taken and grade received.
- What do you hope to get out of this course besides a good grade?
- Do you have any physics questions you’ve always wondered about like: what is a black hole? Is time
travel really possible? What is “relativity”? or “quantum physics”? or “if the Universe is filled with
stars, why is it dark in space but not on Earth?” or the classic “Did Einstein really fail his math class?”
2. Okay, remember how in chemistry they use symbols like “O” for oxygen and “H” for...

...for 1s from 1.6m to 0.2m
it remained at rest for 2s at 0.2m
it moved in the positive direction with a constant speed for 3s’
DISCUSSIONS
I found out that the main of this experiment which is from the experiment I can say that the slope of the distance vs time graph is the velocity of the object the experiment graphs show certain properties which tells whether the object is moving in the negative direction or whether it is moving in the positive direction , if the object is at rest or if it is in motion. If the slope of the graph is increasing it means the object is moving away for the motion detector and if it is decreasing the person is moving towards the motion detector and if the slope is 0 the person is at rest
REFERENCE
Physic for engineers and scientist-serway and jewatt
...

...introduced. Record the voltage and turn on “Plot”.
3.7V
4) This line is much like a line on a geologic topo map. Explain the similarity.
These two are sounded by the curve.
5) You are on the side of a hill with a topo map of the region. If you walked so that your trip follows a topo line you would be doing no work on your backpack. Why?.
Because on that line the height is the same, therefore, there will be no work on the backpack.
6) If a second charge were placed on this line (don’t do it), how much work is need to move it along the line?
Potential is defined that it is equal to minus the work done, and it doesn't change if it's an equipotential.
The force and field are at right angles to an equipotential surface.
7) Move the meter closer to the charge at the center of the screen. What is the new electric potential? Turn on plot again
3.9V
8) Remember that electric potential is energy per charge (1 volt = 1 Joule/Coulomb). Is electric potential a vector or a scalar?
Scalar
9) If a second positive charge were introduced and moved from the first equipotential line created to the second line (closer to the charge), would this involve positive or negative work?
13) Explain.
10) If the second positive charge were moved away from the first Positive charge, would this involve positive or negative work.
Negative work because as the second charge gets close to the first charge, equipotential line gets smaller....

...Name Jonathan Durichek (RODP) Electric Fields
Go to http://phet.colorado.edu/simulations/sims.php?sim=Electric_Field_Hockey
and click on Run Now.
1. You rub balloons in your hair and then hang them like in the picture below. Explain why you think they move apart and what might affect how far apart they get.
As I rub the balloons in my hair, I am picking up positive charges from my hair, which are electrons. The static charge produced will remain active on the balloons, so when they are stuck to the wall by attraction, and then repel one another. Given that the fundamental laws of nature tells us that no charge can be created nor destroyed, I think of the balloons as holding two magnets with the same negative charge facing one another, causing them to repulsion.
2. Test your ideas using Electric Field Hockey in the Practice mode. Make a table to record your observations about what affects the direction and speed of the puck. Your table should demonstrate that you have run controlled tests with all the variables.
Number of (+) charges
Number of (-) charges
Placement of charge
Relative to hockey puck
Results
Zero charge
Zero charge
Puck doesn’t move
None
0
1
Centered
Puck slows gets drawn toward the goal
0
2
Centered
Puck moves quicker toward the goal
1
0
Centered
Puck slowly moves away from the goal
2
0
Centered
Puck moves quicker away from the goal
3. Reflect on your ideas from question #1 and your data from question #2. How do your...

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Physics Lab Report #7
“Analyzing a Projectile’s Motion”
Name: Fei Huo
Date performed: October 22st, 2014
Period 5
Teacher: Mr. Glasel
Purpose:
The purpose of this lab was to examine the behavior of a projectile’s motion
Introduction:
My Classmates and I were doing experiments in lab about and the distance of an object thrown. We were given formulas to solve the problems. We had to fill in a chart and do some questions.
Procedures:
1. First, my classmates and I were to fill in a chart (in data table) from the graph above.
2. Second, my class discussed about how we were suppose to fill in the chart and talk about how to fill it in.
3. Third, we were provided with formulas that we used to fill in the chart.
4. Fourth, my class and I filled in the average horizontal velocity, average horizontal acceleration, Initial horizontal velocity, average horizontal velocity, average vertical acceleration, and the initial vertical velocity.
5. Fifth, we worked on the questions by explaining each of the questions one by one.
Data:
Time
(sec)
Horizontal pos (m)
Vert pos (m)
time
(sec)
Horiz pos (m)
Vert pos (m)
Horiz vel (m/s)
Vert vel (m/s)
Horiz acc (m/s^2)
Vert acc
(m/s^2)
0.0
0
0
1.0
xxxxxxxx
xxxxxx
xxxx
40.0
xxxxxxx
xxxxxx
1.0
30
35
1.0
30
35
30
30
xxxxxxx
Xxxxxx
2.0
60
60
1.0
30
25
30
20
0
-10-10
3.0
90
75
1.0
30
15
30
10
0
-10
4.0
120
80
1.0
30
5
30
0
0
-10
5.0
150
75
1.0
30
-5
30
-10
0
-10
6.0
180
60
1.0
30
-15
30...