4/8/08, 2:55 PM LECTURE CH 4 Forces and Newton's Laws of Motion Rev 1 PAGE 19 OF 50
College Physics 1 Assignments
Website: http://people.rit.edu/abesps1
· PLEASE SIGN THE ATTENDANCE SHEET
GO TO MY WEBSITE…
https://people.rit.edu/abesps1
www.masteringphysics.com
College Physics 1 (211) Instructor: Dr. Alan Entenberg, Office 8-3206, 475-5148 (office), 475-2421 (Physics Dept.),
Email Website for course www.rit.edu/~abesps1 Website for HW www.masteringphysics.com
Schedule Tentative Lecture Workshop Workshop
Day Office hours* Sect 04 and 05 Section 04 Section 05
Mon 2:00 – 2:50 PM 4:00 – 6:00 Noon, 8-3305
Tues 2:00 – 2:50 PM 4:00 – 6:00 PM, 8-3345 6:00 – 8:00 PM, 8-3345
Wed 2:00 – 2:50 PM
Thursday 2:00 – 2:50 PM 4:00 – 6:00 PM, 8-3345 6:00 – 8:00 PM, 8-3345
Friday** 2:00 – 2:50 PM (Bates Study Center, COS)
*Office hours: You are welcome to come by at anytime. One on one meetings in my office can be scheduled if you are unable to make the above posted office hours.
**Office hour will be in the College of Science Bates Study Center. The Center is open every day and is staffed by physics faculty, graduate students, and upper level physics majors. The schedule of the Center is posted on the door.
MORE HELP from Academic Support Center: www.rit.edu/asc See this link for tutoring in Math and Physics in room 01-2371.
Monday (10-7), Tuesday (10-9), Wednesday (10-9), Thursday (10-4), Friday (10-2)
Course Prerequisites: Competency in algebra, geometry, and trigonometry and passing grade in College Physics 1
Course Goals
(1) Understand and use derived concepts of force, energy, and momentum based on the fundamental concepts of matter, space, and time.
(2) Describe motion of an object in horizontal and/or “free-fall” motions near the surface of the earth.
Course Text: COLLEGE PHYSICS: A Strategic Approach by Knight, Jones, and Field, Pearson/Addison Wesley, 2007.
Chapter 1 Concepts of Motion and Mathematical Background Read: Sections 1 – 7
Chapter 2 Motion in One Dimension Read: Sections 1 – 7
Chapter 3 Vectors and Motion in Two Dimensions Read: Sections 1 – 8
Chapter 4 Forces and Newton’s Laws of Motion Read: Sections 1 – 8
Chapter 5 Applying Newton’s Laws Read: Sections 1 – 5, 6 – 8 wait!
Chapter 6 Circular Motion, Orbits, and Gravity Read: Sections 1 – 7
Chapter 7 Rotational Motion Read: Sections 1 – 6
Chapter 8 Equilibrium and Elasticity Read: Sections 1 – 4
Chapter 9 Momentum Read: Sections 1 – 7
Chapter 10 Energy and Work Read: Sections 1 – 10
Homework: You will be assigned about ten problems each week. Some of these will be from the HW website www.masteringphysics.com associated with your text.
Grading (VERY TENTATIVE WEIGHTING): A ( > 90%) B ( > 80%) C ( > 65%) D ( > 55%)
Homework 15 %
Exams 1, 2, 3 (lowest replaced by Final Exam) 50 % Exam1 - March 31, 2008
Final Exam 20 % Cumulative
Activities – 15 %
Attendance ???
Bonus points (for catching my mistakes made in class) Each point worth about 0.1% on course average).
A FORMULA SHEET WILL BE SUPPLIED FOR EACH EXAM and FOR the joint common FINAL EXAM.
Makeup policy---
· It is not possible to makeup an exam. The lowest exam is replaced by the final exam.
· MAKEUP MUST BE SCHEDULED IN ADVANCE
· IMMEDIATE NOTIFICATION OF A VERIFIABLE ILLNESS
· Your academic advisor must also contact me and explain!
· It is not possible to makeup an activity. The lowest activity will be dropped.
WHEN POSSIBLE, AN OPPORTUNITY TO DO THE ACTIVITY WILL BE GIVEN.
· There is a automatic online deduction of 10% for each day that a homework assignment is late.
Lecture/Workshop / Date / Schedule and Equipment Needs
L1 / 3/10/08 / Introduction to the course. Discuss units; conversion of units; dimensional analysis; displacement; average velocity; average acceleration; and motion diagrams (1D only).
W1 / 3/11/08 / “Estimation”
“Unit conversion”
W2 / 3/13/08 / “Basic Measurements and Uncertainties Homework” due
Discuss uncertainties and error analysis.
“Basic Measurements and Uncertainties”
Need: 14 aluminum cylinders of varying volumes, 7 triple beam balances, 7 rulers, 7 electronic calipers
L2 / 3/17/08 / Discuss instantaneous velocity; instantaneous acceleration; position versus time, velocity versus time, and acceleration versus time graphs; trigonometry; vectors and scalars; and 2D kinematics.
W3 / 3/18/08 / “Position-Time and Velocity-Time graphs”
“Logger Pro Tutorial” due
“Introduction to LabPro and the Force Sensor”
Need 14: force sensors with hook, 50 g hangers, mass sets
“Acceleration and Deceleration (1D)”
W4 / 3/20/08 / “Motion diagrams and Motion Graphs”
L3 / 3/24/08 / Discuss free-body diagrams; the gravitational force; the normal force; the tension force; the frictional force; and the spring force. Use “One Dimensional Forces, Translational Equilibrium, Free Body Diagrams” activity as part of discussion.
W5 / 3/25/08 / “Ball Drop Homework” due
DEMO: “Penny/feather”, need apparatus with pump
DEMO: two balls – one dropped and the other fired horizontally, need apparatus
“Ball Drop”
Need 14: motion detectors and small, well inflated soccer balls
W6 / 3/27/08 / “Vector Algebra and Static Translational Equilibrium Homework” due
“Vector Algebra and Static Translational Equilibrium”
Need: 14 force tables (already set up), 14 mass sets, lots of small 1 g, 2 g, etc. masses for use in determining uncertainty in hanging mass
L4 / 3/31/08 / Exam 1. Discuss Newton’s laws.
W7 / 4/1/08 / “Interaction Forces”
Need: 2 force sensors attached to low friction carts, one 500 g mass bar, and one 1.2 m short track per group
W8 / 4/3/08 / “Newton’s Second Law”
Need 14 set ups: accelerometer attached to force sensor which is attached to a low friction cart (arrow on accelerometer points away from force sensor hook), short track
L5 / 4/7/08 / Discuss uniform circular motion; universal gravitation; and non-uniform circular motion.
W9 / 4/8/08 / “Newton’s Second Law Problems”
W10 / 4/10/08 / “Motion in 2D (circular track)”
Need 42: rulers and protractors
L6 / 4/14/08 / Exam 2. Discuss rotational kinematics.
W11 / 4/15/08 / “Uniform Circular Motion”
Need 14: centripetal force apparatus (already set up), stop watches, rulers, 50 g hangers, mass sets,
Need: 7 digital scales, lots of small 1 g, 2 g, etc. masses for use in determining uncertainty in hanging mass
W12 / 4/17/08 / “Rotational Kinematics”
Need 14: RMS with aluminum disk attached, crash box
Need: 7 blue mass sets, spools of string, scissors
L7 / 4/21/08 / Discuss torque; center-of-gravity; moment of inertia; Newton’s second law in rotational form; torque and equilibrium; the spring force; and stress and strain. Use “Torque Calculation” activity as part of discussion.
W13 / 4/22/08 / “Torque and Moment of Inertia”
Need 14: RMS with aluminum disk attached, crash box, calipers, rulers
Need: 7 blue mass sets, 7 digital scales, and spools of string
W14 / 4/24/08 / “Torque and Equilibrium”
Need 14: meter sticks with drilled holes, 0-5 N and 0-50 N spring scales, 50 g hangers
Need: spools of string, scissors, masking tape
L8 / 4/28/08 / Discuss impulse; linear momentum; conservation of linear momentum; inelastic collisions; angular momentum; and conservation of angular momentum.
W15 / 4/29/08 / “Angular Momentum - Qualitative”
Need: 7 low friction bike wheels, 7 platforms, two 500 g mass bars
W16 / 5/1/08 / Discuss work; kinetic energy; work-kinetic energy theorem; work done by gravity; work done by an applied force; and conservative forces. Use “Conservative and Non-conservative Forces” activity as part of discussion.
L9 / 5/5/08 / Exam 3. Discuss potential energy; mechanical energy; mechanical energy conservation; work done by variable forces; and elastic potential energy.
W17 / 5/6/08 / “Energy Graphs”
W18 / 5/8/08 / DEMO: “Rotational energy and Rolling Motion”
Need set up of two inclined planes; hoop/disk of same radius rolling down one incline and back up another.
“Energy Conservation”
Need 14: RMS with aluminum disk attached, crash box
Need: 7 blue mass sets, spools of string, scissors
L10 / 5/12/08 / Discuss energy in collisions and power.
W19 / 5/13/08 / “Rotational Collision”
Need 14: RMS with two aluminum disks and specialty brass pin, rulers
Need: 7 digital scales
W20 / 5/15/08 / Open (“One Dimensional Collision”?)
· What is a single “force” on a given object by a given source?
· A force is a “push” or a “pull” on an object of mass M.
Two types of forces
· 1. Contact forces One object touches another object
Normal force
Tension force
Friction force
o Static friction
o Kinetic friction or sliding friction
Two types of forces continued
· 2. Action at a distance forces force seems to act through “empty space”
o Gravitational force
o Electric and magnetic forces “interaction forces between charges”
Fundamental particles electron, proton, neutron
More fundamental proton and neutron are composites of quarks
o Nuclear (strong) and nuclear (weak) forces
PRINCIPLE OF LINEAR SUPERPOSITION FOR FORCES
What is a “net force” on an object?
· All of the forces on an object add instantaneously to a single net force.
· The “resultant force” or “net force” is obtained in the same way a resultant displacement vector is obtained.
NOTE: ZERO NET FORCE DOES NOT MEAN THERE ARE NO FORCES ON AN OBJECT!!
· Parallelogram rule for only 2 forces
· Pretend force vectors are same as displacement vectors when adding
4/8/08, 2:55 PM LECTURE CH 4 Forces and Newton's Laws of Motion Rev 1 PAGE 19 OF 50
NEWTON’S FIRST LAW:
· ENABLES US TO DETERMINE WHETHER THERE IS A “NET FORCE” ON AN OBJECT. (paraphrased below by abe)
EXPERIMENTAL FACT “An object in motion (constant velocity) stays in motion (constant velocity) unless acted upon by a net force.”
· The constant velocity is non-zero.
EXPERIMENTAL FACT “An object at rest stays at rest unless acted upon by a net force.”
· The constant velocity can even be zero.
“If there is a net force on an object, the velocity must change, i.e., the object must accelerate.”
NEWTON’S THIRD LAW: ALL FORCES OCCUR IN PAIRS!!
§ “THERE IS NO SUCH THING AS AN ISOLATED FORCE!!”
Your Name (Print): Date:
Group Members:
Group:
Interaction Forces (Modified)
You will explore the relationship between the forces that two interacting objects exert on each other.
A force is a push or pull that one body exerts on another. When two bodies interact, they exert forces on each other. When you push down on the table with your hand, the table pushes up on your hand, an effect you can feel. This pushing force is an example of a contact force since the two objects are in contact with each other. As another example, when you drop a pencil, the earth exerts a gravitational force on the pencil pulling it vertically down while the pencil exerts an upward force on the earth. This gravitational force is an example of a non-contact force (or a so called “action-at-a-distance” force) since the two objects do not have to be in physical contact in order to exert the force. Isolated forces do not exist; forces always exist in pairs. Nothing can exert a force without having a force exerted on it.
PREDICTION
Two objects, a truck on the left and a car on the right, can move on a horizontal surface. When the truck and car are in contact, there is a horizontal contact force between them, meaning that the truck pushes on the car and the car pushes on the truck. All motion is along a straight line. You are to compare the magnitudes of these two forces in the different situations described in Table 1.
In parts (a) through (d), assume the vehicles are of equal weight. In parts (e) through (i), assume the truck is much heavier than the car. Discuss and debate your predictions with the others in your group until you reach a consensus. Record the group’s consensus decision in the second column of Table 1 using “less than” (<), “greater than” (>) or “equal to” (=) signs.
Magnitude of the
Force on truck by car is
( , = or < )
the magnitude of the
Force on car by truck / MEASUREMENT
(performed after
all Predictions
are recorded) / Explain Reasoning below
(a) Equal weights; truck (active) pushes against car (passive) but there is no motion.
(b) Equal weight; car (active) pushes against truck (passive) but there is no motion.
(c) Equal weight; Truck (more active) pushes car (passive) to the right, both are moving to the right.
(d) Equal weight; Car (more active) pushes truck (passive) to the left, both are moving to the left.
(e) Heavy truck (active) pushes on light car (passive) to the right but there is no motion.
(f) Light car (active) pushes on heavy truck (passive) to the left but there is no motion.
(g) Heavy truck (more active) moves to the right and collides with a light car (passive) that is at rest (in neutral). They separate after the collision.
MEASUREMENT:
· Connect two force sensors to CH1 and CH2 of the LabPro interface.
· Connect the LabPro interface to the computer.
§ Define the truck as the sensor connected to CH1, and the car as the sensor connected to CH2.
§ Be sure the slide switch on the force sensors is at +50N.
· Open the Logger Pro software. Manually set up the sensors if they do not auto-ID.
§ Reverse the sign of sensor#1 (Experiment->Set Up Sensors->Show All Interfaces, left click the CH1 sensor icon, check Reverse Direction).