Unit 4: Newton’s Laws of Motion

I. Sir Isaac NewtonBio Websites: http://www.maths.tcd.ie/pub/HistMath/People/Newton/RouseBall/RB_Newton.html

http://www.newton.ac.uk/newtlife.html ***Pictures: http://www-history.mcs.st-andrews.ac.uk/PictDisplay/Newton.html

II. Weight versus MassA. Mass is the amount of matter an object or entity consists of.

1. Measured in kilograms (base unit)2. An object’s mass is constant, regardless of its location

B. Weight is the measure of the gravitational force on an object.1. Measured in Newtons and pounds (lbs. – Latin abbreviation for Libras)2. W = mg3. An object’s weight varies, depending on its location.Handout: Gravitational Forces Tables.doc4. The further away an object is from the dictating object’s COG, the lower the

gravitational field strength and weight.a. Earth’s non-spherical shape (wider at the equator) due to rotationb. altitude

C. Conversions1.

Unit Mass WeightMetric kg NEnglish lbs-m (slugs) lbs-f

2. Conversions between kg and lbs. in the Unit Conversion Table are based on the average

Earth gravitational field strength of 9.8066 .

Class Activity: Mass vs. weight.doc

III. Newton’s First Law of MotionA. An object in motion will remain in motion and an object at rest will remain at rest unless

acted upon by a net external force. (i.e., inertia or ΣF = 0)YouTube - High Speed Balloon BounceYouTube - Brainiac's - Things but very slowly - compilation part 1(0:00,2:34,3:34,4:24)YouTube - Slow motion high FPS compilation(1:35,2:08,2:58.3:30,3:46,5:45)B. If no net external force is acting on an object, then ΣF= 0. The object is said to be in

equilibrium in such a case.1. Static equilibrium is typically achieved for objects that we do not want to move

(buildings, bridges, supports, etc.; however, there must be some room allowed for movement for these objects in order to not become brittle/inflexible)

2. If ΣF ≠ 0, then a net external force is present, which will alter the motion of the object.

3. A Free-Body Diagram (FBD) shows all the forces acting on an object. In the FBD, the object and its surroundings are not significant. The emphasis in put on the force vectors.

Sample Problems: Newton’s First Law of Motion Sample Problems 1 and 2.pptx

Assignment: Newtons 1st Law Worksheet.doc

Website: KIDS: How do Airplanes FlyLab/Activity: paper airplane experiment.doc

IV. Newton’s Second Law of MotionA. The sum of all forces on an object is equal to the product of the object’s mass and

acceleration. (i.e., ΣF = ma) B. Newton’s Second Law of Motion blankets Newton’s First Law of Motion due to the fact that

an object in equilibrium will have no acceleration, thus ΣF = 0.C. If an object’s motion is changing, then it is either accelerating or decelerating. This is caused

by a net external force acting on the object.D. The greater the mass of an object, the greater it’s inertia. Therefore, a greater force is

required to accelerate the object.

Sample Problems: Newton’s Second Law of Motion Sample Problems 1, 2, and 3.pptxAssignment: Newton's 2nd Law of Motion Worksheet.docAssignment: Pg.113-114 #’s 67,68,70,72,74 and Pg.142 #’s 85-86

Quiz: Newton's Laws of Motion Quiz.doc

V. Newton’s Third Law of MotionA. For every action there is an equal but opposite reaction (i.e., action and reaction)B. A support reaction force must be present in order for static equilibrium to exist when a net

external force is applied to an object.Sample Problems: Static Equilibrium Sample Problems 1 and 2.pptx

Assignment: Static Equilibrium Worksheet.docGusset Plate Pictures: http://www.taproot.com/wordpress/wp-content/uploads/2007/10/content-2007-08-09-20070809-gussetplate-2.jpghttp://images.publicradio.org/content/2008/03/24/20080324_bent_33.jpghttp://www.garrettsbridges.com/images/whoopingcreek12.jpg

VI. Force of FrictionA. Friction always opposes the motion of an object parallel to the surface on which the

movement is occurring. Ff = µFn

B. A normal force (Fn) is present, which is always perpendicular to the surface on which the movement is occurring.

C. The coefficient of friction between two surfaces is determined through experimentation, and represented by the Greek letter mu (µ).

1. The coefficient of static friction, µs, exists when an object is stationary and a force is applied to move the object along a surface. a. In such a case ΣFx ≥ 0.b. The sum of forces along the surface of movement (typically in the x-dir.) will remain

equal to zero if the pushing force(s) are not great enough to overcome the force of friction. The object will remain stationary, i.e., in equilibrium.

2. The coefficient of kinetic friction, µk, exists when an object is in motion and a force is applied to either accelerate or decelerate the object. a. In such a case ΣFx = mab. The sum of forces along the surface of movement (typically in the x-dir.) will follow

Newton’s Second Law due to the fact that a change in motion will occur. 3. Coefficients are typically less than 1 (but not always) and always greater than 0. The

greater the coefficient, the greater the force of friction. Coefficient of Friction Table on Pg. 129Website: http://frictioncenter.siu.edu/databaseSearch.htmlWebsite: http://www.roymech.co.uk/Useful_Tables/Tribology/co_of_frict.htmVideo: YouTube - Christmas Vacation saucer sled scene (Clark Griswold Super Sled)

Sample Problems: Newton's 3rd Law Worksheet.docSample Problems: Force of Friction Sample Problems 1 and 2.pptx

Assignment: Force of Friction Worksheet.docLab: Coefficient of Friction Experiment.docAssignment: P.142-144 #’s 90-94, 104-106

Extra-Credit Assignment: Sir Isaac Newton Extra-Credit Assignment.docSir Isaac Newton Extra-Credit Assignment Answers.doc

Test Review: Newton's Laws of Motion Test Review.doc

Test: Newton's Law of Motion Test.doc

Content Expectations:

P1.1A P2.1g P3.1AP1.1B P3.1dP1.1C P3.2AP1.1D P3.2CP1.1E P3.2dP1.1f P3.3AP1.1g P3.3bP1.1h P3.3cP1.1i P3.4AP1.2A P3.4BP1.2C P3.4CP1.2D P3.6BP1.2E P3.6CP1.2f

P1.2gP1.2hP1.2iP1.2jP1.2k