Unit 1: Basics and 1D Motion Objectives: Understand selected metric units and prefixes and know how to find them on the NYS Reference Tables Be able to set up and calculate simple conversions Identify difference between scalar/vector, distance/displacement, speed/velocity Define acceleration and perform calculations using its equation Perform calculations using given equations for 1D motion Perform calculations for free falling problems

I. Measuring & Units Precise: repeated measurements/ calculations that show similar results Accurate: degree of correctness High accuracy, low precision High precision, low accuracy

I. Measuring & Units Length m Mass kg Base Units – standard unit of measurement The three base units we will use the most in this course are: SI Base Units Base Quantity Base Unit Symbol Length meter m Mass kilogram kg second s Time

I. Measuring & Units Remember: We will only be using the metric system in this course, so here are some useful ways of relating the English System (US’s measurement) to the rest of the world 1 kg = 2.20 lb = approximate mass of a textbook (175 lb person = 79 kg) 1 m = 3.28 ft = approximate height of a doorknob (a basketball hoop (10ft) = 3.05 m)

I. Measuring & Units Derived Units: Combination of base units Example: m/s, miles/hr Velocity/speed are measured in _____________ m/s/s Acceleration is measured in _________ 5

II. Metric System Metric system has two parts: 1. 2. 1. 2. Prefixes multiply or divide the base units by multiples of _______________ Powers of Ten Video (9 min) Base Unit Prefixes 10 6

Metric Prefixes 1 ms = 0.001 s k 1000 kilo- thousand 1 kg = 1,000 g Symbol Meaning As a number Example k 1000 kilo- thousand 1 kg = 1,000 g 0.01 1 cL = 0.01 L hundredth centi- c m 0.001 milli- thousandth 1 ms = 0.001 s Are Imperial units outdated? (3 min) Time to switch to Metric (3 min) 7

II. Metric System Conversion Practice   1. A common race is the 5 K, which is 5 kilometers. How many meters is this? Given Units: Units Wanted: Conversion scale: Set up and answer: 8

II. Metric System Conversion Practice   2. The recommended daily requirement of vitamin C is 0.5 g. How many milligrams is this? Given Units: Units Wanted: Conversion scale: Set up and answer: 9

II. Metric System Practice Problems 1. 0.553 km 3,000 m 0.50 m 100 mA 0.003 kg 10

1 Dimension Kinematics Trailer Here are some of the things we will be studying during this part of the unit 11

III. Scalar vs. Vector Quantity: Scalar Quantity: A measurement/quantity that has just ________________   Examples: Vector Quantity: A measurement/quantity that has ______________ and __________  Despicable Me Vector MAGNITUDE (SIZE) time, temperature, distance, speed, mass, energy DIRECTION MAGNITUDE velocity, acceleration, force, momentum 12

IV. Distance vs Displacement: SCALAR Distance: ____________ quantity; Total ____________ of path traveled   Displacement: __________ quantity, Change in __________ (Final – initial position) LENGTH VECTOR POSITION 13

IV. Distance vs Displacement: Example: Joe has a date with Jill. Her house is 5 km east of his, but he has to do some things before he picks her up. He first heads 7 km N of his house to get flowers. He then travels 5 km east to pick up the movie tickets. Then he heads to her house.   What was the distance he traveled? What was his displacement? 14

IV. Distance vs Displacement: Example: Usain “Lightning” Bolt runs around the track (400 m) in a time of 44.0 s.   What was the distance he traveled? What was his displacement? 15

V. Speed vs. Velocity: SCALAR v = speed (m/s) d = distance (m) Speed: ____________ quantity; How fast an object is moving (If you are traveling 80 mph, how does it take you to travel 80 miles…)   Equation: Instantaneous Speed: Speed at an given instant (what your speedometer gives you) v = speed (m/s) d = distance (m) t = time (s) 16

V. Speed vs. Velocity: Instantaneous Speed: Speed at an given instant (what your speedometer gives you) Example: What is the average speed of a cheetah that sprints 100 m in 4s?   17

V. Speed vs. Velocity: Example: A car moves with a speed of 30 m/s. Answer the following:   How far would it travel if it moved at this speed for 30 s? How far would it travel if it moved at this speed of 60 s? 18

V. Speed vs. Velocity: Example: If a car moves at 20 m/s, how long does it take for it to travel 500 m?   19

V. Speed vs. Velocity: VECTOR DIRECTION Velocity: ____________ quantity; Speed with _____________________   Example: A car drives around a circular track at a constant speed of 65 mph. Is its velocity changing? Explain VECTOR DIRECTION YES! Same speed (65 mph), but it is changing its direction. 20

V. Speed vs. Velocity: YES, Same speed (100 mph). Example: The speedometer of a car moving to the east reads 100 km/hr. It passes another car that moves to the west at 100 km/hr.   Do both cars have the same speed? Explain Do both cars have the same velocity? Explain YES, Same speed (100 mph). NO, they are moving at OPPOSITE DIRECTIONS 21

VI. Speed vs. Velocity: Practice Problems:   Speed is the rate at which what happens? 2. What is the difference between speed and velocity? 3.Calculate the average speed of a bird flying 140 meters in 5 seconds. 4. A boy is running 5 m/s. How far does the boy run after 15 s? 5. A man walks 3 m east then 2 m west. What is the distance he traveled? What is the man’s displacement? (Hint: Sketch out the man’s path) Distance changes Speed is scalar (just magnitude), velocity is a vector (magnitude and direction) 28 m/s 75 m Distance = 5 m, Displacement = 1 m East 22

VI. Acceleration: __________________ quantity VECTOR   How quickly __________________ changes Acceleration Equations (see reference table): Units: VECTOR VELOCITY a = acceleration (m/s/s or m/s2) v = velocity (m/s) t = time (s) m/s/s or m/s2 23

VI. Acceleration: HOW TO COMPLETE ANY PHYSICS PROBLEM: 1. List givens List what you want to find Find correct equation and manipulate it to solve for desired variable Plug in numbers with units   Examples: A car starts from rest and reaches a speed of 55 m/s in 10 s. What is the car’s acceleration? Givens: Equation: Want: 24

VI. Acceleration: A car is traveling 55 m/s and comes to a stop in 10 s. What is the car’s acceleration?   Givens: Equation: Want: Jeff Gordon is going 20 m/s and pushes down on the gas pedal and accelerates at 5 m/s2 for 7 s. What is his final speed? A car is accelerated at 4.0 m/s2 from rest. When will the car reach a speed of 28 m/s? 25

VI. Acceleration: A car is accelerated at 4.0 m/s2 from rest. When will the car reach a speed of 28 m/s?   Givens: Equation: Want: 26

VII. Free Fall & Acceleration due to Gravity: Definition – acceleration due to gravity is the acceleration of an object in free fall that results from the influence on Earth’s force of gravity Acceleration is a ______________ quantity (_______________ AND _______________) Acceleration due to gravity on Earth = ____________ All objects (regardless of _________ and ____________) fall at the ____________ acceleration (IGNORING AIR RESISTANCE) (Falcon feather on the moon)   VECTOR MAGNITUDE DIRECTION 10 m/s/s MASS SIZE SAME 27

VII. Free Fall & Acceleration due to Gravity: t = 0 s, v = 0 m/s t = 1 s, v = 10 m/s t = 2 s, v = 20 m/s   t = 3 s, v = 30 m/s t = 4 s, v = 40 m/s 10 m/s/s t = 5 s, v = 50 m/s 28

VII. Free Fall & Acceleration due to Gravity: Penny of the Empire State Building - Mythbusters   29

VII. Free Fall & Acceleration due to Gravity: Example: A 4 kg ball is dropped from rest and reaches a speed of 20 m/s. Find the time it took to reach this speed.   Givens: Set up and Answer Want: Would the time change if it was a 2 kg ball? (World’s Biggest Vacuum Chamber Video 4 min) NO! MASS DOES NOT AFFECT THE RATE OF FALLING 30

VII. Free Fall & Acceleration due to Gravity: 1. A 70 kg skydiver falls out of a plane. Determine his final speed if he falls for 2.5 s.   2. How do you think the acceleration due to gravity on the moon compares to that of Earth? Explains in terms of size (mass) comparison between Earth and Moon. 3. While on a mysterious planet an astronaut drops a feather from a height of 1 m. If the feather lands in 0.75 s with a speed of 1.79 m/s, determine the acceleration due to gravity on the planet. 4. Based on your answer to question 3, how do you think the size (mass) of the mysterious planet compares to Earth? 25 m/s The moon is much less because of its smaller mass compared to Earth 2.39 m/s/s Smaller because of its smaller acceleration due to gravity 31

VII. Free Fall & Acceleration due to Gravity: Felix Baumgartner World Record Jump (4 min) Laso Schaller World Record Platform jump (2 min) (article) 32