 Large scale  Small scale  Fast vs. slow  Frame of reference?

 Objects change in position relative to a reference point. › Reference point should be stationary

Distance Displacement  Total length which an object moves  Can be a straight line, but doesn’t have to be  Doesn’t have a particular direction  Change in position of an object  Straight line from the starting point to the final point  MUST BE A STRAIGHT LINE!!!  Shorter or equal to distance, never more  Must have a particular direction (toward/away)

John’s house Jane’s house School A C B

 Speed – the distance traveled in a given amount of time  To calculate speed, must know both distance and time › Speed = distance/time speed = d/t › (SI Units)  Distance – meters (m)  Time – seconds (s)  m/s

 SPEED = DISTANCE TIME DISTANCE = 315 laps TIME = 3 hours SPEED = ? Track length = 1 mile

V s t

 Constant speed – object covers equal distances in equal amounts of time (doesn’t change) › Example: earth’s rotation  Most objects don’t have constant speed

 X-axis – independent variable  Y-axis – dependent variable  Time is usually independent b/c it will pass whether distance is traveled or not  Constant speed is a straight line  The slope (rise/run) give the speed of the object  Steeper the slope, the faster the speed

 Average speed = distance / time  Instantaneous speed – speed at that very instant › Example - speedometer  Constant speed – doesn’t change › Example – Earth’s rotation

 Speed in a certain direction  Used for navigation, weather  Direction can be N, S, E, or W of a fixed point  Negative or positive along the line of motion  Velocity = displacement (m) / time (s)  SI units › m/s

 The speed of these racers may not have changed… Explain why their velocity has changed.

 Can add 2 velocities that are going same direction to get resultant velocities  If moving in opposite directions, you subtract to get the resultant velocity

V d t

 Any change in velocity  Change in direction causes acceleration › Examples – moon, race track

 Positive acceleration – object is speeding up › Examples: a car goes from 0mi/hr to 60 mi/hr in 3 seconds.  Negative acceleration – object is slowing down › Example: skier stopping from 20m/s in.5s

 Acceleration can be determined by the change in velocity over a change in time ACCELERATION = FINAL VELOCITY – INITIAL VELOCITY TIME a = (v f - v i )/(t f - t i )  SI units: › (m/s)-(m/s) / s = m/s 2

 Identify two conditions that must be met for these joggers to be at zero acceleration. 1. No change of direction. 2. No change (increase/decrease) in speed.

 Acceleration can be determined by a velocity-time graph › The slope of the line gives you the value of acceleration › Positive slope – object is speeding up (positive acceleration)

› Negative slope – object is slowing down (negative acceleration) › Horizontal line – velocity is not changing, thus the acceleration is 0m/s 2

 Force – an action which changes an objects state of rest or motion › Has magnitude and direction  Examples of FORCES: › Gravity › Friction › Engines

 Net force – combination of all the forces acting on an object › If net force =0, the object is balanced  Doesn’t move › If net force is unbalanced, object accelerates in the direction which force is greater

 Friction – force that acts against a motion in progress › Constant force has to be applied to an object to keep it moving  Example: car will eventually stop, if gas is not applied › Friction also affects stationary object  Example: truck parked on hill – friction of brakes provides a force against gravity

Static Friction Kinetic Friction  Friction b/w 2 stationary surfaces  Greater than kinetic  Friction b/w 2 moving surfaces  Less than static b/c it takes more force to make an object start moving than to keep it moving  Sliding friction – 2 objects slide past each other  Rolling friction – round object rolls over a flat surface › Usually less than sliding

 Air resistance opposes motion › Example: as a car moves, it must push the air out of the way › The easier the air is pushed out of the way, the faster it will go › Designing the shape of the car so that less air must be displaced is called streamlining

Harmful Helpful  Road rash  Carpet burn  Wear and tear on car tires  Racing  Air hockey  B/w road and tires makes driving possible  Sand on icy roads  Stopping a car  Racing

Sir Isaac Newton described the relationship b/w motion and force in 3 laws

 An object at rest remains at rest and an object in motion maintains its velocity unless it experiences an unbalanced force. › Example: as car stops suddenly, body keeps moving  Inertia – tendency of an object to resist a change in velocity (speed & direction) until acted upon

 Inertia is related to mass of an object › Object with small mass has less inertia than object with large mass  Example: softball & bowling ball  Other examples of inertia: › Lean toward side around curves › Seatbelts keep you from continuing to move › Car seat has a more equal distribution of weight keeping baby safe

 The unbalanced force acting on an object equals the objects mass times its acceleration  Force=mass x acceleration F=ma  SI unit › Newtons (N) = Kg x m/s 2

 Example: empty grocery cart vs. full cart

 Law of Universal Gravitation – all objects in the universe attract each other through gravitational force Force = G (m 1 x m 2 /d 2 ) G=6.673 x N x m 2 /kg 2  Gravitational force increases as 1 or both masses increase  Gravitational force decreases as distance b/w masses increase

 Acceleration depends on the mass of the object and the unbalanced force applied › More mass – harder to accelerate › More force – faster acceleration

 When gravity is the only force acting on an object it is in free fall › If there were no air resistance, all objects would fall to the Earth at the same speed:  9.8m/s 2 (acceleration due to gravity)

 Weight is the force of gravity on an object Weight = mass x gravity w = mg  SI unit is Newton (N) › Kg x m/s 2

 The mass of an object is always the same, but weight changes as gravity changes. › Example: an astronaut has a mass of 66kg. What is his weight on Earth and on the moon? On the moon gravity is 1.6 m/s 2

 The force of gravity is constant: › Air resistance increases as you fall › It eventually equals force of gravity › Equal force of gravity & air = 0 acceleration › No acceleration means constant velocity (max) called terminal velocity

 Orbiting objects are in free fall: › Move forward then free fall toward other object  Projectile motion – curved path that an object follows when thrown, launched, or projected › Combination of forward horizontal motion and downward horizontal motion

 For every action force, there is an equal and opposite reaction force.  Can occur when there is no motion: › Example: sitting in chair  Or can occur in motion: › Example: rocket

 Momentum- the product of the mass & velocity of an object momentum = mass x velocity p = mv  Si Units  Kg x m/s  Has direction because velocity has direction  When force changes motion, momentum changes as well

 Example: calculate the momentum of a 6 kg bowling ball moving at 10m/s down the alley toward the pins.

 Law of Conservation of Momentum: › The total amount of momentum is a system is conserved › Used to predict motion of cars after a collision