PHYSICS Lecture 2-Motion Chapter 3 Southern Boone County High School Bill Palmer

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