Thursday, 1/24 & Friday, 1/25
-go over homework problems
-Forces quiz #1
Tuesday, 1/29 & Wednesday, 1/30
-go over friction notes
-work friction and forces problems
Thursday, 1/31 & Friday, 2/1
-go over friction homework
-Forces Quiz #2
-if you give blood at the blood frive on Feb. 7, you may
earn 15 bonus points
-permisssion forms to donate blood are due by 1/31
-if you are incapable or unwilling (a needle!!) of donating
blood, you can write a short paper, create a poster, or a
short (5 or so slides) powerpoint presentation on blood,
its uses, how its processed, etc.
-you will also be getting a handout on a Black History
Month bonus project this week
Some Forces Notes
kinematics: the study of how objects move
dynamics: the study of why objects move
force: a push or a pull; a vector quantity
The four types of Forces
gravitational force: an attractive force that exists between all objects; the weakest of all the forces
electromagnetic force: the force that results from a basic property of particles called electric charge; gives materials their strength, ability to bend, etc.; very large compared to gravitational force.
strong nuclear force: the force that holds the nucleus of an atom together; probably the strongest of the four forces.
weak force: the force involved in the radioactive decay of some nuclei; not well understood.
Newton's Laws of Motion
Newton's First Law of Motion
An object with no net force acting on it remains at rest or moves with a constant velocity in a straight line. The method of finding the net force is to sum all of the forces, keeping track of the signs(remember, positive for forces to the right and negative for forces to the left). This is also known as the Law of Inertia.
Inertia is the property of matter that resists change in motion. The inertia of an object is prpoprtional to its mass. A large mass tends to resist changes in its motion to a greater extent than a smaller mass.
Newton's Second Law of Motion
The acceleration of a body is directly proportional to the net force on it and inversley proportional to its mass. this is usually written as F = ma where
F = the force exerted on an object in units of Newtons m = the mass of the object in kg
a = the acceleration of the object in m/s/s
Newton: the unit of force, equal to the amount of force that causes a mass of 1 kg to accelerate at a rate of 1 meter per second squared.
What is the net force required to accelerate a 1000.0 kg car at 2.6 m/s/s?
solution F = ma
F = (1000)(2.6) = 2600 N
a 5.00 kg bowling ball is accelerated from rest to a velocity of 11.0 m/s as the bowler covers 4.80 m of approach before releasing the ball. What average force is exerted on the ball during this time?
solution: F = ma, vf(squared)- vi(squared) = 2ad
We must first find the acceleration to plug into Newton's second law of motion, so we need to rearrange one of the above formulas to get:
a = [vf(squared) - vi(squared)]/2d
a=[(11.0 * 11.0) - (0 * 0)] / 2(4.80)
a = 121 / 9.60 = 12.6 m/s/s
Now that we have acceleration, we can plug it into the basic formula to find the force.
F = ma
F = 5.00 * 12.6 = 63.0 N
Forces Problems #1
#1An object with a mass if 10 Kg is at rest. A net force of 20 N is applied. What is the final velocity? How far with the object have moved in the 10 s interval?
During a circus performance, Brad Hill is fired from a cannon that is 20 m long at a rate of 40 m/s. If Brad's mass is 70 Kg, find the average force on him during the firing of the cannon.
A force of 10 N is applied to a 4.0 Kg block that is at rest on a perfectly smooth, level surface. Find the acceleration of the block.
A 2000 Kg car accelerates from 10 m/s to 30 m/s in 6s. What is the force on the car?
A certain force gives a 5 Kg object an acceleration of 2.0 m/s(squared). What acceleration would the same force give a 20 Kg object?
Mrs. Witt's Classroom Expectations
Welcome to my science class. Forget all of the bad things that you have heard about science and prepare to work hard and have fun!
I will make frequent use of the internet. Class agendas, assignments, quizzes, etc. will be posted at this and other announced web-sites. If you don't have a computer at home, remember that you can access these sites from any computer at the school and the public library. If you and/or your parents have an email address, please send it to me so that I can send you reminders and updates.
I am at school by 8:00 a.m. and I don't leave until 4:00 p.m. You may call me at home at 383-6142. Parents and students can also schedule an appointment with me through the guidance office by calling the school at 664-8190. Both my home and school email addresses are listed above and can be used. Please allow me a day or two to respond.
A. All assignments are to be completed on time or there will be a penalty.
B. Keep a record of all assignment grades on the grade sheet that I will give you, which should be in the front of your portfolio.
A. All lab reports should follow the given lab report template.
B. Graded labs should be kept in your folder and are fair game for lab or notebook quizzes.
C. Any violation of lab safety will be dealt with strictly.
D. All students are required to have a signed safety contract on file before they are allowed to participate in lab.
E. Missed labs must be made up after school within 5 school days.
A. There will be NO communication with anyone other than myself during tests.
B. Only assigned materials will be used during a test.
C. No graphing calculators are allowed on any test.
D. Tests are largely problem oriented; strictly memorizing information won't get you a passing grade.
E. Generally, tests are worth twice as much as the homework/classwork material that the test covers.
A. The Friday on the week after a test, there will be a retest.
B. The retest will not be exactly the same test, but it will be very similar (same number and types of questions, same difficulty level, etc.)
C. The retest will always be after school. NO EXCEPTIONS.
D. If you cannot stay after school on Fridays, then make sure you do well on the test the first time.
A. I use the total point system, so the importance of a particular assignment can be determined by the number of points that it is given.
B. You will be given a grade sheet to use to keep track of your grades, so you should be able to tell what your grade is at any given time. So don't ask me!
C. Each grade will be given as points earned/possible points. Divide the top score by the bottom score and multiply the result by 100 to determine your grade on that item.
D. Add up the top scores from all of your assignments. Add up the bottom scores from all of your assignments. Divide the total top by the total bottom and multiply the result by 100. This will give you your class grade at that time.
F. The lowest daily grade will be dropped at the end of each 9 weeks.
A. There will be at least one or more major projects during the year.
B. Information, including requirements and grading scale, will be provided later.
A. Every student will be required to maintain a portfolio.
B. The portfolio will be kept in a three ring binder with dividers between each chapter/section.
C. At the beginning of each chapter/section you will be given a portfolio assignment sheet that will explain and list all of the assignments.
D. The portfolio will be turned in a week after the test over the material in that chapter/section and will usually be returned within a week.
E. Each portfolio chapter/section will be a separate grade, usually roughly equivalent to the test in points.
F. You pick which level of portfolio that you complete. Everyone is required to complete the C level (which is basically a notebook), but you can choose to complete extra assignments to earn a B or an A on the portfolio.
G. B and A level assignments that were completed and turned in on time, but did not meet the grade requirement to be counted towards your portfolio will be returned to you. You will have one week to correct/redo the assignment and turn it in again for credit. This basically means that anyone who really wants to can earn an A on each portfolio!
A. You are expected to take an active role in discussions, activities, and especially group work.
B. You are expected to exhibit mature behavior and to treat others with courtesy and respect.
C. Offenses will be dealt with according to the severity and/or frequency of the problem.
D. All district and school policies must be followed at all times.
E. You will be given two passes to the bathroom per semester.
IX. Required Supplies
A. 3-ring notebook with dividers.
B. Scientific (not graphing) calculator.
C. Paper, pens, and other supplies that you might need, including Kleenex.
A. All school and district polices must be followed.
B. You are responsible for all missed material and work, I will not keep up with your assignments for you.
LET'S HAVE A GREAT YEAR!!!!
- fun mini-quiz on Newton's laws and Star Trek
- games reviewing Newton's laws
- games involving forces and friction
- games that review some basic terms on forces
- games on simple forces terminology
- 10 question quiz on force, motion, acceleration, etc.
- multiple choice quiz on forces and friction
- to-the-point introduction to Newton's laws
- explains Newton's laws, weight, mass, and friction, and has interactive questions
- excellent site on forces, with a quiz, examples, and notes
- another very good site on Newton's laws with notes, animations, and quizzes
|Last updated 2008/09/28 11:12:13 EDT||Hits 151|