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Transcript
Speed/Motion Notes! • Motion – an object is in motion if it changes position to a reference point • r=d/t • Constant speed g speed does not change • Average speed g speed changing (total distance/total time) • Instantaneous speed g the speed of an object at any given instant 0.31 0.85 0.97 1.06 1.53 1.95 2.47 2.71 3.54 3.89 4.03 4.55 4.78 5.28 5.91 6.44 6.79 7.03 7.67 What is the average speed of this bowling ball? S=d/t S=19m/7.67sec S=2.48m/sec Distance vs. Time Distance (meters) distance time 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 15 10 5 0 0 1 2 3 4 5 Time (sec) 6 7 8 9 Slope and Speed Distance (m) Distance vs Time Which trial has the greatest slope? 40 30 20 10 0 Trial 1 Trial 2 Trial 3 0 5 Time (sec) 10 Which trial travels the farthest in the 10 seconds? Which trial has the fastest speed? Slope = y/x = distance/time = Speed Is short for “change in” SLOPE = SPEED!!!!!! • Time= • Distance= distance/speed speed*time • A lion runs at 50mph for .5 hr. How far does he travel? • d=r*t • d=50 mi/hr*.5hr • d=25 mi • An elephant runs at 25mph for 50 mi. How long does it take to get where he is going? • t=d/r • t=50mi/ 25mi/hr • t=2 hr A hyena travels for 30 mi. for .75 hr. How fast is the hyena traveling? r=d/t r= 30mi./.75hr r= 40 mi./hr Velocity • Velocity g speed and direction! o •Boat a 6 mph east •River c 4 mph east •Velocity=6 mph east+ 4mph east •V= 10 mph east •River b 4mph west •Velocity=6mph east– 4mph west •V= 2mph east Ferris Wheel The speed is constant but it is always changing velocity because it is always changing direction! http://www.ies.co.jp/math/java/trig/kanran/kanran.html ferris wheel Acceleration The rate at which velocity changes. This can be an increase in velocity (acceleration) This can be a decrease in velocity (deceleration or negative acceleration) A=(final velocity-initial velocity)/time A=(Vf-Vi)/t What is the acceleration of a car that goes from 0 to 60mi/hr in 10 sec.? A=(vf-vi)/t A= (60mi/hr)/10 sec. A=6 mi/hr/sec. What is the acceleration of a car that slows down from 70mi/hr to 25 mi/hr in 15 sec.? A=(vf-vi)/t A=(25mi/hr-70mi/hr)/15 sec. A=-45mi/hr/15sec. A=-3mi/hr/sec A roller coaster is constantly accelerating because the velocity is always changing! What is the acceleration of a roller coaster that starts with a velocity of 4 m/s and accelerates to 22m/s in 3 sec.? A=(22m/s-4m/s)/3s A=18m/s//3s A=6m/s/s or 6m/s2 Gravity! Gravity: a force that pulls objects together. Freefall: a falling object with no other force but gravity acting upon it. Acceleration due to gravity is 9.8m/s/s The person jumps off the plane. What is his speed at 1 sec? 2 sec? 3 sec? Terminal Velocity! The maximum velocity a falling object can achieve. The air resistance equals the force of gravity so the object does not accelerate any more. http://hypertextbook.com/facts/JianHuang.shtml