Physical Science Physical Science Chapter 11 Motion Chapter pg.328Chapter 11 Motion Chapter pg.328

11.1 Distance and Displacement 11.2 Speed and Velocity 11.3 Acceleration

Richard E. Clemons M.S. MNHHS MARCH., 2008

Motion Motion

Are we in this room in Motion? Y or N

Both answers are correct due to the following reasons;

A) no because our position to the floor, walls, and ceiling is not changing

B) yes, as a part of the earth we are rotating and revolving constantly

11.1 pg.328 11.1 pg.328 Distance & DisplacementDistance & Displacement

All forms of motion has to be judged by an outside factor

The concept is based on a frame of reference or a reference object

These reference items are best chosen as items that under NORMAL conditions can not move

Reference Reference

A reference object is any object that we can use to define determine if a change in an objects position has occurred

Any object that can move under normal conditions is NOT the best choice to use for determining motion

Best items; those that normally Stationary usually the ones that are attached to the Earths surface

Examples; trees buildings road signs

Relative motionRelative motion

All motion is relative until proof of that movement can be presented

That is a change in the objects position as compared to a reference item attached to the earth

This motion can then be measured for distance moved and the time it took that distance to be covered

Distance Distance

Is the measured value that connects two points when in a straight line the calculation is simple

A line is shortest distance between two points

Standard unit for length (dist) in science is the METER and we add prefixes for longer or shorter values

SI / Metric system for distanceSI / Metric system for distance

Base unit METER Prefixes

Larger value Giga = billion Mega = million Kilo = thousand

Smaller value Deci = 1/10 Centi = 1/100 Milli = 1/1000

QuantityQuantity

Information that is obtained and provides us with specific data places for analysis

This data provided falls into two categories

A) Scalar quantity

B) Vector quantity

Scalar QuantityScalar Quantity

A description of an item that is focused on One factor only

The focus is on MAGNITUDE Magnitude is a measurement value,

thus it must have a number an label Single dimension (definite quantity) Time, temperature, length, mass,

direction

Vector QuantityVector Quantity

A description of an item that contains TWO components of information

Like a scalar quantity it also contains a magnitude value

Unlike a scalar quantity a vector also includes a second component, direction

Vectors are then Magnitude with Direction

Displacement Displacement

This item is a two part factor for motion A) distance B) direction When both distance and direction are

combined it can provide a large amount of information

5Km or 5Km to the East Which one is best for providing a direction

to a stranger to your area?

Resultant vectorResultant vector

The resultant vector is the vector that is produced that equals the sum of the vectors involved in the problem

That is, gets you from the starting point to the ending point in the shortest distance or the new velocity and direction caused by the interaction of multiple vectors on an object

Resultant vectorResultant vector

There are four methods that we will focus on for solving multiple vectors of interaction

A) adding B) subtracting C) Pythagorean theorem a2

+ b2 = c2 written as r2 = a2 + b2

D) law of cosines r2 = a2 + b2 – 2abcos(theta)

Solving vectorsSolving vectors

Adding Combine the two values by adding if

and only if the parts are going in the same direction

Subtract Combine the two values by subtracting

if and only if the parts are going in the opposite direction

Solving vectorsSolving vectors

Pythagorean theorem If the two parts form a right angle and

the finishing side completes a right triangle

Law of Cosines Use for any vector that does not fit the

other styles and when the final side is added you have created a triangle that is acute and/or obtuse (any style other than a right triangle)

Distance: Displacements Along a Line

Figure 3

Distance: Displacements Along a Line

Figure 3

Distance: Displacements Along a Line

Figure 3

Distance: Displacements Along a Line

Figure 3

Distance: Displacements Along a Line

Figure 3

Speed or Velocity sect 11.2 pg 332Speed or Velocity sect 11.2 pg 332

The math portion is the same equation Rate = distance / time

That is how fast is equal to total distance divided by total time

Since direction will be necessary at some time the term velocity is a better choice

So VELOCITY (V) = DISTANCE (D) / TIME (T)

Calculating Average Speed

Section 11.2

Calculating Average Speed

Section 11.2

Calculating Average Speed

Section 11.2

SLOPE pg 334SLOPE pg 334

On a graph the velocity or rate of motion can be found by finding the slope of a line

Slope = rise / run Slope = change in Y’s/change in X’s

Distance-Time Graphs for Motion of Three Cars

Section 11.2

Acceleration sect 11.3 pg 342Acceleration sect 11.3 pg 342

Acceleration is the rate at which velocity changes against time

How fast the rate is increased or decreased or the direction changes

Acceleration equals final velocity minus starting velocity divided by time

A = VF – VI / t

AccelerationAcceleration

Summary Any change in the following can

technically be a form of acceleration Faster velocity Slower velocity Change to direction

Acceleration Acceleration

Name three items in / on a car that can control acceleration

Gas pedal (accelerator) Brake pedal (decelerator) Steering wheel (change direction)

Measuring Acceleration

Section 11.3

Measuring Acceleration

Section 11.3

Measuring Acceleration

Section 11.3

acceleration graphs pg 346Figures 16 and 17

Distance-Time Graph of Accelerated Motion

Figure 18

Average or Constant or InstantaneousAverage or Constant or Instantaneous

Average is the comparison of TOTALS; total distance / total time

Constant (uniform) NO change in the rate or direction

Instantaneous what is happening at a specific moment (how fast when you look at the speedometer of the car)

Equations Equations

Velocity *V=d/t

*d=v*t *t=d/v

Vectors *Add (same) *subtract

(opposite) *Pythagorean c2= a2 + b2

EquationsEquations

Slope *Slope = rise/run

*slope = y2 – y1 / x2 – x1

Acceleration *a = VF – VI / t *t =

VF – VI /a *v (change) =a*t