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PHYSICSLecture 2-MotionChapter 3
Southern Boone County High School
Bill Palmer
MotionQ: What is motion?A: When something changes position.
Straight Line Circle Arc Back and Forth
Motion-DiagramQ: What is a motion diagram?A: A series of images (points) that
shows how an object has changed position at equal intervals of time.
Think of movie frames.
Motion
What is the runner doing?
Motion-Particle Model
Think of the runner’s belt buckle as a point.
Motion-Particle Model
. . . . . . . . . . . . . . .
. . . . . . .
. . . . . . .
Motion-Coordinate System
Y
XOrigin
What is the runner doing?
Motion-Coordinate System
Y
XOrigin
Gives the zero point and the direction of increase.
Motion-Coordinate System
Y
XOrigin
Origin is point where variables are zero.
Motion-Coordinate System
Y
XOrigin
Now we have a high jumper. Positive numbers are to the right and up.
Motion-Position Vector
Y
XOrigin
Points from origin to location at a particular time.
Motion-Scalar Quantity
Tells only the magnitude of the units. Temperature Time Mass
Motion-Vector Quantity
Tells the magnitude and direction of the units. Maps
Motion-Displacement
The Distance and Direction between two positions.
Motion-Displacement Question: How far is it to Columbia?
What’s wrong with this question??
Motion-Displacement Question: How far is it to Columbia?
What’s wrong with this question??
Well, duh, it doesn’t say from where?
Motion-Time Interval
The change in time between two events.
For example, the start and finish of a race.
delta = Greek letter meaning change
/\t = t1 – t0
Motion-Average Velocity
Average Velocity is the distance divided by the time it takes to go the distance.
_
v = /\t
/\d
Motion-Average Velocity
If a car goes 350 miles in 4.5 hrs what is its average velocity?
V=350m /4.5hr = 77.7 mph
Motion-Average Acceleration
Average acceleration is the change in velocity divided by the change in time.
A = /\v
/\t
Motion-Average Acceleration
A car accelerates from 0 to 100 mph in 15 sec.
A = 100mph-0 = 100 mph = 6.6 mph/s
15-0 s 15s
Motion-Average Acceleration
A car passes another car and accelerates from 45 to 70 mph in 12 sec. What is its average acceleration?
A = 70mph-45 = 25 mph = 2.08 mph/s
12-0 s 12s
Motion-Average Acceleration
A car sees a deer in the road and decelerates from 65 to 5 mph in 4 sec. What is its average acceleration?
A = 5mph – 65 = -60 mph = -15 mph/s
4-0 s 4 s
Motion-Average Acceleration
A car slams into a tree at 85 mph and comes to a dead stop in 1 sec. What is its average acceleration?
Did the driver survive?
Motion-Average Acceleration
A car slams into a tree at 85 mph and comes to a dead stop in 1 sec. What is its average acceleration?
Did the driver survive?No—his heart was ripped out!
Motion-Problems
Problems, page 61-17- 23
Due at EOP
