Chapter 11Motion

Wrap Up F.O.R.

An object or point from which motion is determined?

The most common frame of reference?

Under what conditions might a car moving alongside your car appear to be moving backwards?

Motion Motion – is a change in position relative

to a frame of reference. Motion is measured by distance and time

1. Distance is measured in meters or kilometers.

2. Time is measured in seconds or hours.

Motion Change in position in relation to a

reference point.

Reference point

Motion

Speed

Speed – is the distance traveled by a moving object per unit of time.

speed = distance time

Speed(How fast an object is moving)

For example, 30 miles per hour means object travels distance of 30 miles in an elapsed time of one hour. Write as,

(SPEED) =(Distance traveled)

(Time elapsed)

30 miles per hour = 30 miles

hour

speed = distance time

What is the speed of a jet plane that flies 7200 km in 9 hours?

Step 1 Write down the given information. Step 1 Write out the formula. Step 2 Substitute given numbers and

units Step 3 Solve for unknown variable.

!!!Make sure the units are written!!!

Speed – Distance - Time

How Far? Distance is related to Speed

Distance = Speed x Time

How Long? Time is also related to Speed

Time = Distance

Speed

Self Check

What is the average speed of a cheetah that sprints 100 meters in 4 seconds? How about if it sprints 50 meters in 2 seconds?

In both cases 100/4 = 50/2 = 25 meters/second.

A car has an average speed of 100 kilometers per hour. How far does it travel in 60 minutes?

Distance = (100)x(1 hour) = 100 kilometers.

Your school bus travels 45 mph during a 15 minute ride to school, how far is your ride?

Suppose that you can run 3.5 m/s. How long would it take you to run 11 m?

More speed problems

Suppose that you sprint 100 meters in 9.5 seconds (look out Usain Bolt!), but then slow down a little and run the next 50 meters in 7.3 seconds. What is your overall average speed?

1-23-09 Day 2

Speed Practice Turn In

Graphing Speed

Motion Quiz

Homework Summarize

Notes Complete Slope

WS Read-Highlight-

Answer Read Chapter 11

Section 2

Velocity speed in a given direction.

Velocities in the same direction: (+) Add + = 2m/s E + 1m/s E = 3m/s E

Velocities in different directions: (-) Subtract

+ = 2m/s E - 1m/s W = 1m/s E

ExamplesExamples•EscalatorEscalator•TreadmillTreadmill

Average Velocity

Self checkThe speedometer of a car moving east reads

100 km/h. It passes another car moving west at 100 km/h. Do they have same speed? Velocity?

Same speed but different directions so their velocities are different.

During a certain period of time, the speedometer of a car reads a constant 60 km/h. Does this indicate a constant speed? Constant velocity?

Speed is constant but direction may not be constant so velocity may or may not be constant.

Graphing Motion

Slope – slant of a line connecting two points that indicates the change in the Y axis as compares to the X axis.

The slope of the line is directly related to the speed.

Slope – slant of a line connecting two points that indicates the change in the Y axis as compares to the X axis.

Constant Speed Speed that does

not change.•For constant speed For constant speed the line is straight.the line is straight.

A distance vs. time graph

Average Speed Measure of speed obtained by

dividing the total distance by the total time.

time total

distance totalspeed avg.

Graphing MotionGraphing Motion

slope =

steeper slope =

straight line =

flat line =

Distance-Time Graph

A

B

faster speed

constant speed

no motion

speed

Wrap Up

What is Motion? What is speed? How is it calculated? What is average speed? What is the significance of slope on

a distance-time graph? What is velocity?