I. Newton’s Laws of Motion Ch. 3 & 4 Motion & Forces I. Newton’s Laws of Motion “If I have seen far, it is because I have stood on the shoulders of giants.” - Sir Isaac Newton (referring to Galileo)

A. Newton’s First Law Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force.

F = ma B. Newton’s Second Law Newton’s Second Law of Motion The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. F = ma

C. Newton’s Third Law Newton’s Third Law of Motion When one object exerts a force on a second object, the second object exerts an equal but opposite force on the first.

II. Describing Motion Motion Speed & Velocity Acceleration Ch. 3 & 4 Motion & Forces II. Describing Motion Motion Speed & Velocity Acceleration

Newton’s First Law Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force. motion constant velocity net force

A. Motion Problem: Is your desk moving? We need a reference point... nonmoving point from which motion is measured

A. Motion Motion Change in position in relation to a reference point.

A. Motion Problem: You are a passenger in a car stopped at a stop sign. Out of the corner of your eye, you notice a tree on the side of the road begin to move forward. You have mistakenly set yourself as the reference point.

v d t B. Speed & Velocity Speed rate of motion distance traveled per unit time

B. Speed & Velocity Instantaneous Speed speed at a given instant Average Speed

B. Speed & Velocity Problem: A storm is 10 km away and is moving at a speed of 60 km/h. Should you be worried? It depends on the storm’s direction!

B. Speed & Velocity Velocity speed in a given direction can change even when the speed is constant!

t a C. Acceleration Acceleration the rate of change of velocity vf - vi t Acceleration the rate of change of velocity change in speed or direction a: acceleration vf: final velocity vi: initial velocity t: time

C. Acceleration Positive acceleration “speeding up” Negative acceleration “slowing down”

t d v D. Calculations d = 100 m v = d ÷ t t = 20 s Your neighbor skates at a speed of 4 m/s. You can skate 100 m in 20 s. Who skates faster? GIVEN: d = 100 m t = 20 s v = ? WORK: v = d ÷ t v = (100 m) ÷ (20 s) v = 5 m/s You skate faster! v d t

t a D. Calculations a = (vf - vi) ÷ t t = 3 s A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration? GIVEN: vi = 10 m/s t = 3 s vf = 32 m/s a = ? WORK: a = (vf - vi) ÷ t a = (32m/s - 10m/s) ÷ (3s) a = 22 m/s ÷ 3 s a = 7.3 m/s2 a vf - vi t

t d v D. Calculations v = 330 m/s t = d ÷ v d = 1km = 1000m Sound travels 330 m/s. If a lightning bolt strikes the ground 1 km away from you, how long will it take for you to hear it? GIVEN: v = 330 m/s d = 1km = 1000m t = ? WORK: t = d ÷ v t = (1000 m) ÷ (330 m/s) t = 3.03 s v d t

t a D. Calculations t = ? t = (vf - vi) ÷ a t = (0m/s-30m/s)÷(-3m/s2) How long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s2? GIVEN: t = ? vi = 30 m/s vf = 0 m/s a = -3 m/s2 WORK: t = (vf - vi) ÷ a t = (0m/s-30m/s)÷(-3m/s2) t = -30 m/s ÷ -3m/s2 t = 10 s a vf - vi t

E. Graphing Motion slope = speed steeper slope = straight line = * 07/16/96 E. Graphing Motion Distance-Time Graph A B slope = steeper slope = straight line = flat line = speed faster speed constant speed no motion *

E. Graphing Motion Who started out faster? A (steeper slope) Distance-Time Graph A B Who started out faster? A (steeper slope) Who had a constant speed? A Describe B from 10-20 min. B stopped moving Find their average speeds. A = (2400m) ÷ (30min) A = 80 m/min B = (1200m) ÷ (30min) B = 40 m/min

E. Graphing Motion Distance-Time Graph Acceleration is indicated by a curve on a Distance-Time graph. Changing slope = changing velocity

E. Graphing Motion acceleration slope = +ve = speeds up Speed-Time Graph acceleration +ve = speeds up -ve = slows down slope = straight line = flat line = constant accel. no accel. (constant velocity)

E. Graphing Motion Specify the time period when the object was... Speed-Time Graph Specify the time period when the object was... slowing down 5 to 10 seconds speeding up 0 to 3 seconds moving at a constant speed 3 to 5 seconds not moving 0 & 10 seconds

III. Defining Force Force Newton’s First Law Friction Ch. 3 & 4 Motion & Forces III. Defining Force Force Newton’s First Law Friction

A. Force Force a push or pull that one body exerts on another What forces are being exerted on the football? Fkick Fgrav

A. Force Balanced Forces forces acting on an object that are opposite in direction and equal in size no change in velocity

A. Force Net Force unbalanced forces that are not opposite and equal velocity changes (object accelerates) Fnet Ffriction Fpull N W

B. Newton’s First Law Newton’s First Law of Motion An object at rest will remain at rest and an object in motion will continue moving at a constant velocity unless acted upon by a net force.

B. Newton’s First Law Newton’s First Law of Motion “Law of Inertia” tendency of an object to resist any change in its motion increases as mass increases

Taken from “The Physics Classroom” © Tom Henderson, 1996-2001. ConcepTest 1 TRUE or FALSE? The object shown in the diagram must be at rest since there is no net force acting on it. FALSE! A net force does not cause motion. A net force causes a change in motion, or acceleration. Taken from “The Physics Classroom” © Tom Henderson, 1996-2001.

ConcepTest 2 You are a passenger in a car and not wearing your seat belt. Without increasing or decreasing its speed, the car makes a sharp left turn, and you find yourself colliding with the right-hand door. Which is the correct analysis of the situation? ...

ConcepTest 2 1. Before and after the collision, there is a rightward force pushing you into the door. 2. Starting at the time of collision, the door exerts a leftward force on you. 3. both of the above 4. neither of the above 2. Starting at the time of collision, the door exerts a leftward force on you.

C. Friction Friction force that opposes motion between 2 surfaces depends on the: types of surfaces force between the surfaces

C. Friction Friction is greater... between rough surfaces when there’s a greater force between the surfaces (e.g. more weight) Pros and Cons?

IV. Force & Acceleration Ch. 3 & 4 Motion & Forces IV. Force & Acceleration Newton’s Second Law Gravity Air Resistance Calculations

F = ma A. Newton’s Second Law Newton’s Second Law of Motion The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. F = ma

F = ma F m a F m A. Newton’s Second Law F: force (N) m: mass (kg) a: accel (m/s2) 1 N = 1 kg ·m/s2

B. Gravity Gravity force of attraction between any two objects in the universe increases as... mass increases distance decreases

B. Gravity Who experiences more gravity - the astronaut or the politician? Which exerts more gravity - the Earth or the moon? more mass less distance

W = mg B. Gravity Weight the force of gravity on an object MASS WEIGHT W: weight (N) m: mass (kg) g: acceleration due to gravity (m/s2) MASS always the same (kg) WEIGHT depends on gravity (N)

B. Gravity Would you weigh more on Earth or Jupiter? Jupiter because... greater mass greater gravity greater weight

Animation from “Multimedia Physics Studios.” B. Gravity Accel. due to gravity (g) In the absence of air resistance, all falling objects have the same acceleration! On Earth: g = 9.8 m/s2 elephant feather Animation from “Multimedia Physics Studios.”

C. Air Resistance Air Resistance a.k.a. “fluid friction” or “drag” force that air exerts on a moving object to oppose its motion depends on: speed surface area shape density of fluid

C. Air Resistance Fair Fgrav Terminal Velocity maximum velocity reached by a falling object reached when… Fgrav = Fair Fair no net force  no acceleration  constant velocity Fgrav

Animation from “Multimedia Physics Studios.” C. Air Resistance Terminal Velocity increasing speed  increasing air resistance until… Fair = Fgrav Animation from “Multimedia Physics Studios.”

Animation from “Multimedia Physics Studios.” C. Air Resistance Falling with air resistance heavier objects fall faster because they accelerate to higher speeds before reaching terminal velocity Fgrav = Fair larger Fgrav  need larger Fair  need higher speed Animation from “Multimedia Physics Studios.”

a F m D. Calculations F = ? F = ma m = 40 kg F = (40 kg)(4 m/s2) What force would be required to accelerate a 40 kg mass by 4 m/s2? GIVEN: F = ? m = 40 kg a = 4 m/s2 WORK: F = ma F = (40 kg)(4 m/s2) F = 160 N m F a

a F m D. Calculations m = 4.0 kg a = F ÷ m F = 30 N A 4.0 kg shotput is thrown with 30 N of force. What is its acceleration? GIVEN: m = 4.0 kg F = 30 N a = ? WORK: a = F ÷ m a = (30 N) ÷ (4.0 kg) a = 7.5 m/s2 m F a

a F m D. Calculations F(W) = 557 N m = F ÷ a m = ? Mrs. J. weighs 557 N. What is her mass? GIVEN: F(W) = 557 N m = ? a(g) = 9.8 m/s2 WORK: m = F ÷ a m = (557 N) ÷ (9.8 m/s2) m = 56.8 kg m F a

ConcepTest Is the following statement true or false? An astronaut has less mass on the moon since the moon exerts a weaker gravitational force. False! Mass does not depend on gravity, weight does. The astronaut has less weight on the moon.

V. Nonlinear Motion Projectile Motion Circular Motion Free-fall Ch. 3 & 4 Motion & Forces V. Nonlinear Motion Projectile Motion Circular Motion Free-fall

A. Projectile Motion Projectile any object thrown in the air acted upon only by gravity follows a parabolic path called a trajectory has horizontal and vertical velocities PROJECTILE MINI-LAB

A. Projectile Motion Projectile Velocities Horizontal and vertical velocities are independent of each other!

A. Projectile Motion Horizontal Velocity depends on inertia remains constant Vertical Velocity depends on gravity accelerates downward at 9.8 m/s2

Animation from “Multimedia Physics Studios.” ConcepTest A moving truck launches a ball vertically (relative to the truck). If the truck maintains a constant horizontal velocity after the launch, where will the ball land (ignore air resistance)? A) In front of the truck B) Behind the truck C) In the truck C) In the truck. The horizontal velocity of the ball remains constant and is unaffected by its vertical motion. Animation from “Multimedia Physics Studios.”

B. Circular Motion Centripetal Acceleration acceleration toward the center of a circular path caused by centripetal force B-BALL DEMO PLATE DEMO

B. Circular Motion On the ground... friction provides centripetal force

B. Circular Motion In orbit... gravity provides centripetal force ROUND LAB

Near-Earth Satellites Geostationary Satellites B. Circular Motion In orbit... Which satellites travel faster? Near-Earth Satellites Geostationary Satellites

B. Circular Motion Extra Credit Use the NASA Liftoff web site to find the International Space Station (“STATION”) in the sky this weekend. liftoff.msfc.nasa.gov/realtime/Jpass/20/ Write a brief description of your sighting - time, appearance, & other observations.

C. Free-Fall Free-Fall when an object is influenced only by the force of gravity Weightlessness sensation produced when an object and its surroundings are in free-fall object is not weightless! CUP DEMO

C. Free-Fall Weightlessness surroundings are falling at the same rate so they don’t exert a force on the object

Space Shuttle Missions NASA’s KC-135 - “The Vomit Comet” C. Free-Fall Space Shuttle Missions Go to Space Settlement Video Library. NASA’s KC-135 - “The Vomit Comet” Go to CNN.com. Go to NASA.

ConcepTest 1 TRUE or FALSE: An astronaut on the Space Shuttle feels weightless because there is no gravity in space. FALSE! There is gravity which is causing the Shuttle to free-fall towards the Earth. She feels weightless because she’s free-falling at the same rate.

ConcepTest 2 Describe the path of a marble as it leaves the spiral tube shown below. It will travel in a straight line since the tube is no longer exerting a net force on it.

VI. Action and Reaction Ch. 3 & 4 Motion & Forces Newton’s Third Law Momentum Conservation of Momentum

A. Newton’s Third Law Newton’s Third Law of Motion When one object exerts a force on a second object, the second object exerts an equal but opposite force on the first.

A. Newton’s Third Law Problem: How can a horse pull a cart if the cart is pulling back on the horse with an equal but opposite force? Aren’t these “balanced forces” resulting in no acceleration? NO!!!

A. Newton’s Third Law Explanation: forces are equal and opposite but act on different objects they are not “balanced forces” the movement of the horse depends on the forces acting on the horse

A. Newton’s Third Law Action-Reaction Pairs The hammer exerts a force on the nail to the right. The nail exerts an equal but opposite force on the hammer to the left.

A. Newton’s Third Law Action-Reaction Pairs The rocket exerts a downward force on the exhaust gases. The gases exert an equal but opposite upward force on the rocket. FG FR

A. Newton’s Third Law F m Action-Reaction Pairs Both objects accelerate. The amount of acceleration depends on the mass of the object. F m Small mass  more acceleration Large mass  less acceleration

JET CAR CHALLENGE CHALLENGE: Construct a car that will travel as far as possible (at least 3 meters) using only the following materials. scissors tape 4 plastic lids 2 skewers 2 straws 1 balloon 1 tray How do each of Newton’s Laws apply?

p = mv v p m B. Momentum Momentum quantity of motion p: momentum (kg ·m/s) m: mass (kg) v: velocity (m/s)

v p m B. Momentum p = ? p = mv m = 280 kg p = (280 kg)(3.2 m/s) Find the momentum of a bumper car if it has a total mass of 280 kg and a velocity of 3.2 m/s. GIVEN: p = ? m = 280 kg v = 3.2 m/s WORK: p = mv p = (280 kg)(3.2 m/s) p = 896 kg·m/s m p v

v p m B. Momentum p = 675 kg·m/s v = p ÷ m m = 300 kg The momentum of a second bumper car is 675 kg·m/s. What is its velocity if its total mass is 300 kg? GIVEN: p = 675 kg·m/s m = 300 kg v = ? WORK: v = p ÷ m v = (675 kg·m/s)÷(300 kg) v = 2.25 m/s m p v

C. Conservation of Momentum Law of Conservation of Momentum The total momentum in a group of objects doesn’t change unless outside forces act on the objects. pbefore = pafter

C. Conservation of Momentum Elastic Collision KE is conserved Inelastic Collision KE is not conserved

C. Conservation of Momentum A 5-kg cart traveling at 4.2 m/s strikes a stationary 2-kg cart and they connect. Find their speed after the collision. BEFORE Cart 1: m = 5 kg v = 4.2 m/s Cart 2 : m = 2 kg v = 0 m/s AFTER Cart 1 + 2: m = 7 kg v = ? p = 21 kg·m/s m p v p = 0 v = p ÷ m v = (21 kg·m/s) ÷ (7 kg) v = 3 m/s pbefore = 21 kg·m/s pafter = 21 kg·m/s

C. Conservation of Momentum A 50-kg clown is shot out of a 250-kg cannon at a speed of 20 m/s. What is the recoil speed of the cannon? BEFORE Clown: m = 50 kg v = 0 m/s Cannon: m = 250 kg AFTER Clown: m = 50 kg v = 20 m/s Cannon: m = 250 kg v = ? m/s p = 0 p = 1000 kg·m/s p = 0 p = -1000 kg·m/s pbefore = 0 pafter = 0

C. Conservation of Momentum So…now we can solve for velocity. GIVEN: p = -1000 kg·m/s m = 250 kg v = ? WORK: v = p ÷ m v = (-1000 kg·m/s)÷(250 kg) v = - 4 m/s (4 m/s backwards) m p v

VII. Forces in Fluids Ch. 3 & 4 Motion & Forces Archimedes’ Principle Pascal’s Principle Bernoulli’s Principle

A. Archimedes’ Principle Fluid matter that flows liquids and gases Buoyancy the ability of a fluid to exert an upward force on an object immersed in it

A. Archimedes’ Principle Bouyant Force upward force exerted by a fluid on an immersed object bouyant force > weight balloon rises bouyant force < weight balloon sinks bouyant force = weight balloon floats

A. Archimedes’ Principle the bouyant force on an object in a fluid is equal to the weight of fluid displaced by the object Very little water needs to be displaced in order to cancel weight  ball floats on surface. More water needs to be displaced in order to cancel weight  ball floats lower in the water. Not enough water is displaced in order to cancel weight  ball sinks. View Buoyancy JAVA Applet. View animations produced by students at Poly Prep Country Day School in Brooklyn, New York.

View hydraulics explanation. B. Pascal’s Principle Pascal’s Principle pressure applied to a fluid is transmitted unchanged throughout the fluid View hydraulics explanation.

B. Pascal’s Principle Platform: 1000 N = F2 F = 1000 N 250 m2 10 m2 A car weighing 1000 N sits on a 250 m2 platform. What force is needed on the 10 m2 plunger to keep the car from sinking? GIVEN: Platform: F = 1000 N A = 250 m2 Plunger: F = ? A = 10 m2 WORK: 1000 N = F2 250 m2 10 m2 (1000 N)(10 m2)=(250 m2)F2 F2 = 40 N

C. Bernoulli’s Principle as the velocity of a fluid increases, the pressure exerted by the fluid decreases EX:airplane lift, curve balls

C. Bernoulli’s Principle Airplane lift Curve Ball View airplane wings explanation.

C. Bernoulli’s Principle Funnel Demos View funnel explanation. View inverted funnel explanation.

C. Bernoulli’s Principle Venturi Effect fluids flow faster through narrow spaces causing reduced pressure EX: garden sprayer, atomizer, carburetor

C. Bernoulli’s Principle Venturi Effect - Atomizers View atomizer explanation.