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## Aim: What is the difference between speed & velocity?

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**Date: 10/15/2007**Monday Aim: What is the difference between speed & velocity? Do Now: What is motion? Homework: Read pgs 70 – 73 in textbook & Answer Ques. 1 & 2 on pg 72 (Practice Problems) – Write out Formula, Plug in #’s, Calculate & Give Units**What is motion?**A change in position over a certain amount of time or, The movement of an object**What is speed?**The rate at which an object moves (how fast or slow) How can speed be calculated? Speed = Distance Time D S T**1) Carl Lewis runs a 100 meter race in 10 seconds. What**is his average speed? Avg. Speed = Total distance/Total Time Avg. Speed = 100 m/10 sec Avg. Speed = 10 m/s**2) How much time does it take for a cheetah to travel 84**meters at a speed of 28 m/s? Time = distance/speed T = 84 m 28 m/s T = 3 sec.**3) What distance does a jogger go if she runs with a speed**of 160 m/min for 20 minutes? Distance = speed x time D = (160 m/min) (20 min) D = 3,200 m**What information does a Distance vs. Time Graph show?***Constant Speed: speed that stays the same D I S T A N C E (km) Smith’s Trip to Albany 200 150 100 50 Distance (km) Time (hr) 50 100 150 200 1 2 3 4 1 2 3 4 TIME (hours)**What information does a Distance vs. Time Graph show?***Speed Changes D I S T A N C E (km) Brown’s Trip to Albany 200 150 100 50 Distance (km) Time (hr) 100 100 150 200 1 2 3 4 1 2 3 4 TIME (hours)**What is velocity?**A measure of both speed & direction Example: An automobile travels 80 km North in 2 hrs. What is the avg. speed of the car? What is the avg. velocity? V = 80 km 2 hr Avg. speed = 40 km/hr V = D T Avg. velocity = 40 km/hr North**Date: 10/28/2007**Friday Aim: 1. What does a distance vs. time graph show? 2. How do velocities add & subtract from each other? Do Now: 1. Take out homework. 2. What is the slope of a distance vs. time graph equal to? Homework: Handout (A Speedy Journey)**20 km (40 km – 20 km)**0.5 h or 30 min 40 km (80 km – 40 km) 1.5 hrs.**5. What is car B’s**avg. speed during the first part of this trip? Avg. S = T. Dist. T. Time Avg. S = 40 km 0.5 hr Avg. S = 80 km/hr 6. How fast did cars A & B go together? Avg. S = T. Dist. T. Time Avg. S = 40 km 1 hr Avg. S = 40 km/hr**A = VF – VI**time 12 km / 20 s = 0.60 km/s A = 0.67 – 0.60 10 20 km / 30 s = 0.67 km/s .007 km/s2 30 km / 40 s = 0.75 km/s A = 0.93 – 0.75 20 56 km / 60 s = 0.93 km/s .009 km/s2 NO**Can velocities add together?**Yes, but only if they’re moving in the same direction Example: If you are paddling a boat South at 5 m/s & the stream is moving at 8 m/s South: Are their velocities adding together? Your boat will move at: 13 m/s South**Can velocities subtract from each other?**Yes, but only if they’re moving in the opposite direction Example: If you are paddling a boat South at 10 m/s & the stream is moving North at 12 m/s: Your boat will move: 2 m/s North**What does each picture show?**Velocities adding together 6 m/s Right 10 m/s Right 16 m/s Right + = Velocities subtracting 14 m/s Left 4 m/s Left 10 m/s Right = -**Date: 10/17/2006**Wednesday Aim: Lab: Measuring the Speeds of People Walking Do Now: 1. Take out homework. 2. Read over lab 3. Answer ques. next slide. Homework: Complete Lab**Aim: How can we calculate acceleration?**Do Now: 1. Take out Lab & Motion Note-packet 2. Complete Review Questions on pg 6 in your note-packet Homework:Handout**#1**#4 #1 None All 4 cars are moving at constant speed Avg. Speed = T. Dist./T. Time __________= 250 km/1 hr 250 km/hr**What is acceleration?**The rate at which the velocity of a moving object increases What is the mathematical formula for acceleration? Acceleration =change in velocity time OR a = vfinal – vinitial t**1) What is the acceleration of an ice skater who changes**velocity from 5 m/s north to 15 m/s north in 5 seconds? a = 15 m/s – 5 m/s 5 s a = vfinal – vinitial t a = 2 m/s2 North**2) How quickly would a race car accelerate if its velocity**changed from 0 to 32 m/s in 4 seconds? a = 32 m/s – 0 m/s 4 s a = vfinal – vinitial t a = 8 m/s2**What is deceleration?**The rate at which the velocity of a moving object decreases**What information does a Velocity vs. Time Graph show?***Constant acceleration V E L O C I T Y (M/S) Smith’s Trip to Albany 28 21 14 7 Velocity (m/s) Time (s) 7 14 21 28 1 2 3 4 1 2 3 4 TIME (hours)**What is the motion**of a freely falling object? Any object falling near the surface of the earth will accelerate at a rate of 9.8 m/s2 due to the pull of gravity.**Date: 10/19/2007**Friday Aim: What is Momentum? Do Now: Prepare for Motion Quiz Homework: Study for next week’s Exam on Motion & Forces**What is momentum?**The mass of an object multiplied by its velocity, which determines how difficult it is to stop the object. The greater the momentum = greater energy the object has What is the mathematical formula for momentum? momentum = mass x velocity or p = mv**Date: 10/22/2007**Monday Aim: 1. What is Force? Do Now: 1. What 2 things does momentum depend upon? 2. What are units of momentum? Homework: Study for a Quiz on Forces.**What is a Force?**A push or a pull that one object exerts on another. What are some examples of a force? Ex) A tow truck pulls a car, The wind pushes a flag, Gravity & Friction What is a Newton? The unit used to measure force Force = Mass X Acceleration 1N = kg.m/sec2**The attractive force between objects**What is gravitational force? • Depends on the masses of the objects and the distance between them As mass increases, gravitational pull increases As distance increases, gravitational pull decreases**Where is the Gravitational Pull the greatest?**50 kg 1. 10 kg 10 m 2. 10 kg 10 kg 10 m**Where is the Gravitational Pull the greatest?**1. 10 kg 10 kg 10 m 2. 10 kg 10 kg 20 m**What is weight?**The weight of an object is equal to the gravitational force exerted by Earth (9.8m/s2) on an object Where will you weigh more: on the Earth or on the Moon? Why?**Forces on an object that are equal in size & opposite in**direction What are balanced forces? = 0 - The net force is zero because the two forces cancel each other out**Unequal forces working against each other produces motion in**the direction of the larger force. What are unbalanced forces? 10N = 6N - 4N *In Opposite Directions, Forces Subtract**Date: 10/23/2007**Tuesday Aim: 1. What is Newton’s First Law of Motion? Do Now: Prepare for a Quiz. Homework: Read pgs 98 – 103 & Ans. Ques. (1-4 & 6-7) on pg 103 (self-check)**Newton’sLaws**of MotionJ**The Law of Inertia**What is Newton’s 1st Law of Motion? 1. Objects at rest tend to stay at rest unless acted upon by an unbalanced force. 2. Objects in motion tend to remain in motion (in constant velocity, along a straight path) unless acted upon by an unbalanced force. (such as friction)**This is what happens when your not wearing a seatbelt. Since**the car is in motion you are also in motion, and when the wall stops the car.You continue to be in motion and fly forward.**When the truck is stopped by the car. The ladder continues**in motion.**The tendency of an object to resist a change in motion.**What is inertia? Inertia is related to an objects mass: the more mass an object has the greater its inertia and the more difficult it is to change its motion. Which would have more inertia an empty shopping cart or a full one?**Date: 10/24/2007**Wednesday Aim: 1. What are 3 types of friction? Do Now: 1. Take out homework. 2. What is Newton’s First Law of Motion? Homework: Read pgs 104-111 Ans. Ques. (1-4 & 6) on pg 111 (self check)**Exists wherever 2 surfaces touch.**What is friction? • It’s a force that acts in the opposite direction to motion. • It causes moving objects to slow down & stop. • It always produces heat.