2 A. Motion Motion Change in position in relation to a reference point.
3 A. Motion Problem: How fast is the bumblebee flying? We need a frame of reference...nonmoving point from which motion is measured.What could be used as a frame of reference in the illustration above?
4 Example:1. Describe the motion of the fish in the cat’s frame of reference.2. Describe the motion of the cat in the fish’s frame of reference.3. Which one is “really” moving; the cat or the fish?
5 RELATIVE MOTION:Movement in relation to a frame of reference.EX: Passengers on a rollercoaster appear to onlookers on the ground to be speeding by
7 Yet, when the people on the roller coaster look at each other, they don’t appear to be moving at all
8 A. Motion Consider the following scenario: 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.
9 Choosing a meaningful frame of reference is important in clearly describing motion!
10 A. Motion Distance Length of a path Choose a unit with appropriate sizeSI unit: meter (m)Long distances = kmShort lengths = cm, mm
11 A. Motion Displacement Distance and direction from starting point The Millenium Force roller coaster travels 6,595 ft throughout the ride (distance)It’s total displacement is zero!
12 A. Motion Vector Has magnitude (size, length, amount) and direction. Shown as an arrow pointing in an appropriate direction (up, down, N, S, etc); length shows magnitudeVector
13 A. MotionExample 1:A fire truck drives 10 miles East, then turns around and drives 2 miles West.Displacement = 10 miles EDisplacement = 2 miles WSum Vector/Disp. = 8 miles E
14 A. MotionExample 2:The school bus travels 2 miles East, then stops to pick up students, and continues to travel an additional 3 miles East.3 miles E2 miles EResultant Vector/ Total Disp. = 5 miles E
15 v d t B. Speed & Velocity Speed rate of motion distance traveled per unit time
16 B. Speed & Velocity Instantaneous Speed speed at a given instant Average Speed
17 B. Speed & Velocity Problem: You are driving down Olio road, look at your speedometer, and realize you’re going 80 mph. A cop clocks you. Has he measured your average or instantaneous speed?Instantaneous! You weren’t driving 80 mph the entire trip!
18 B. Speed & Velocity Problem: Your family is driving to Florida for a vacation. The trip is 1200 miles long and it takes 20 hours to get there. Is 60 mph your instantaneous speed?No! You probably sped up, slowed down, stopped for gas, or stopped to eat at several instances during the trip.
19 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!
20 B. Speed & Velocity Velocity speed in a given direction can change even when the speed is constant!
21 t d v C. 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 mt = 20 sv = ?WORK:v = d ÷ tv = (100 m) ÷ (20 s)v = 5 m/sYou skate faster!vdt
22 t d v C. 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/sd = 1km = 1000mt = ?WORK:t = d ÷ vt = (1000 m) ÷ (330 m/s)t = 3.03 svdt
23 t d v C. Calculations v = 5.7 km/y d = v x t t = 15 y The slowest animal ever discovered traveled with a speed of 5.7 km/y. How far would the crab travel in 15 y?GIVEN:v = 5.7 km/yt = 15 yd = ?WORK:d = v x td = (5.7 km/y) x (15 y)d = 85.5 kmvdt
24 C. CalculationsWhat is the speed of the Mediterranean crab from problem #3 in meters per day?GIVEN:v = 5.7 km/y= ? m/dayWORK:5.7 km/y x (1 mi/1.6 km) x (1 y/365 days) =d = mi/day
25 t a D. Acceleration Acceleration the rate of change of velocity vf - vitAccelerationthe rate of change of velocitychange in speed or directiona: accelerationvf: final velocityvi: initial velocityt: time
26 D. Acceleration Positive acceleration “speeding up” Negative acceleration“slowing down”
27 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/st = 3 svf = 32 m/sa = ?WORK:a = (vf - vi) ÷ ta = (32m/s - 10m/s) ÷ (3s)a = 22 m/s ÷ 3 sa = 7.3 m/s2avf - vit
28 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/svf = 0 m/sa = -3 m/s2WORK:t = (vf - vi) ÷ at = (0m/s-30m/s)÷(-3m/s2)t = -30 m/s ÷ -3m/s2t = 10 savf - vit
29 E. Graphing Motion slope = speed steeper slope = straight line = *07/16/96E. Graphing MotionDistance-Time GraphABslope =steeper slope =straight line =flat line =speedfaster speedconstant speedno motion*
30 E. Graphing Motion Who started out faster? A (steeper slope) Distance-Time GraphABWho started out faster?A (steeper slope)Who had a constant speed?ADescribe B from min.B stopped movingFind their average speeds.A = (2400m) ÷ (30min) A = 80 m/minB = (1200m) ÷ (30min) B = 40 m/min
31 E. Graphing MotionDistance-Time GraphAcceleration is indicated by a curve on a Distance-Time graph.Changing slope = changing velocity
32 E. Graphing Motion acceleration slope = +ve = speeds up Speed-Time Graphacceleration+ve = speeds up-ve = slows downslope =straight line =flat line =constant accel.no accel. (constant velocity)
33 E. Graphing Motion Specify the time period when the object was... Speed-Time GraphSpecify the time period when the object was...slowing down5 to 10 secondsspeeding up0 to 3 secondsmoving at a constant speed3 to 5 secondsnot moving0 & 10 seconds
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