speed, velocity, distance and displacement

1. Speed & VelocitySpeed & Velocity
Intro to Mechanics - The Study of MotionIntro to Mechanics - The Study of Motion

2. In your lab notebook, please answer as best you can:
1. What direction should the decimal point be moved when
converting from mm to km?
• Left (6 places)
2. How many decibels is 0.0385 hectobels?
• 38.5 dB
3. Convert 30 meters into feet. (1 m≈ 3.3 ft)
• 99 ft
4. Convert 150 lb into kg. (1kg ≈ 2.2 lb)
• 68.2 lb
4. What speed is 45 m/s in miles per hour? (1 km ≈ 0.6 mi)
• 97.2 mph
Bonus Question: What is “DIMENSIONAL ANALYSIS” and what is it used for?
Dimensional analysis is a method of using equivalent fractions to convert units of measurement..
Review
Quiz 23

3. What is Motion?What is Motion?
 Motion = a change in positionMotion = a change in position
 An eagle flies from its nest to a tree branchAn eagle flies from its nest to a tree branch
 A man pushes a box of cookies across his deskA man pushes a box of cookies across his desk
 An elevator moves from the lobby to 25An elevator moves from the lobby to 25thth
floorfloor

4. All Motion is RelativeAll Motion is Relative
 Reference pointReference point
 Change in position depends on an object thatChange in position depends on an object that
is referred to:is referred to:
 man is moving relative to ground but NOT relativeman is moving relative to ground but NOT relative
to train carto train car

5. SpeedSpeed
 Speed measures the rate at which aSpeed measures the rate at which a
change in position occurschange in position occurs
Speed =Speed = distancedistance
timetime
Banana Slugs: 0.75 inches/hour
Average Highway Speed: 65 mph
Eye Blinks: 0.005 centimeter/millisecond
Earth’s Orbit: 30 km/s
Speed of Light: 300,000,000 meters/second

6. Rates & RatiosRates & Ratios
 What does 65 mph mean?What does 65 mph mean?
65 miles65 miles
1 hour1 hour
 How far will I travel with a speed of 25 m/s if IHow far will I travel with a speed of 25 m/s if I
go for 2 hours?go for 2 hours?
25 meters25 meters x 7,200 s = 180,000 mx 7,200 s = 180,000 m (180 km)(180 km)
1 second1 second
* The line in any fraction or ratio means DIVIDE!* The line in any fraction or ratio means DIVIDE!
65 miles
Speed x time = distanceSpeed x time = distance

7. SpeedSpeed
 Constant speedConstant speed: speed remains the same for: speed remains the same for
entire distance travelledentire distance travelled
 Instantaneous speedInstantaneous speed: speed at one given instant: speed at one given instant
 Average speedAverage speed: total distance/total time: total distance/total time
15 meters in 145 seconds = .1 m/s15 meters in 145 seconds = .1 m/s
1 meter in 5 seconds = .2 m/s
2 meters in 8 seconds = .25 m/s
1 meter in 10 seconds = .1 m/s
2 meters in 30 seconds = .07 m/s
3 meters in 17 seconds = .18 m/s
3 meters in 60 seconds = .05 m/s
3 meters in 15 seconds = .2 m/s

8. Displacement vs. DistanceDisplacement vs. Distance
 DistanceDistance: how far something moved: how far something moved
 8.2km + 1.8km + 4.5km = 14.5 kilometers8.2km + 1.8km + 4.5km = 14.5 kilometers
 DisplacementDisplacement: shortest distance between: shortest distance between
starting point and ending pointstarting point and ending point
 2.7 km North2.7 km North *includes direction**includes direction*
 DistanceDistance is ais a scalarscalar measuremeasure
 DisplacementDisplacement is ais a vectorvector measuremeasure
because it includes directionbecause it includes direction

9. Graphing SpeedGraphing Speed
Time in Seconds
DistanceinMeters
1 meter in 5 seconds = .2 m/s
2 meters in 8 seconds = .25 m/s
1 meter in 10 seconds = .1 m/s
2 meters in 30 seconds = .07 m/s
3 meters in 17 seconds = .18 m/s
3 meters in 60 seconds = .05 m/s
3 meters in 15 seconds = .2 m/s
Average speed = .1 m/s

10. Slope = SpeedSlope = Speed
Time in Seconds
DistanceinMeters

11. Experiment 24
Distance-Time Graphs
Distance Time
Calculated
Speed
Trial 1
Trial 2
Trial 3
1)Design your experiment
to minimize variables.
2)Measure the distance
traveled and time
traveled.
 RECORD THE
VALUES IN A TABLE.
1)Calculate the speed in
each trial using:
2)Graph your data with
distance on the y-axis
and time on the x-axis.
 Include all trials on the
same graph

13. Displacement – Time GraphsDisplacement – Time Graphs
1) Where did the runner start?
2) At what position did the runner
stop? (relative to what?)
3) Does the graph show distance
or displacement?
4) How long did it take the runner to
get to their final position?
5) What can you tell about the
speed of the runner?
6) What does a negative slope
indicate?
7) How would this graph change if
the y-axis showed total distance
instead of displacement?

14. VelocityVelocity
 Velocity = Speed + DirectionVelocity = Speed + Direction
 A vector quantityA vector quantity
 SpeedSpeed: 32 m/s: 32 m/s
 VelocityVelocity: 32 m/s: 32 m/s SoutheastSoutheast
 Why does direction matter?Why does direction matter?

15. Transportation QuandaryTransportation Quandary
 You must get from Kyoto to Nagano forYou must get from Kyoto to Nagano for watchwatch
the world figure skating championships.the world figure skating championships.
 The Bullet Train travels East & West at speeds over 350 km/hr.The Bullet Train travels East & West at speeds over 350 km/hr.
 A personal tachikoma can go up to 85 km/hr in any direction.A personal tachikoma can go up to 85 km/hr in any direction.
 Solar cell buses move North & South at 60 km/hr.Solar cell buses move North & South at 60 km/hr.
 A hired Pivo taxi will take you 105 km/hr NE or 125 km/hr SW.A hired Pivo taxi will take you 105 km/hr NE or 125 km/hr SW.
 Which mode of transportation should you take?Which mode of transportation should you take?