1. Applied Physics 11 Speed

2. Common Units Distance/Displacement Meter (m) Time Seconds (s) Minutes (min) = 60s Hours (h) = 60 min, 3600s Days (d) = 24h Years (yr) = 365d Speed/Velocity Meters/second (m/s) Kilometers/hour (km/h) Acceleration Meters/second/second (m/s 2 )

3. Speed To calculate speed, you need to know both distance and time Objects that travel at different speeds move different distances in the same amount of time Speed can be calculated by dividing the distance an object travels by the time it takes to cover the distance The formula for finding speed is Speed = distance/time v=d/t

4. Conversions 1km=1000m 100cm=1m 100 000cm=1km

5. Metric Conversion GMkh da.dcm μ n giga mega kilo hecta deca Base Unit deci centi milli micro nano billions millions thousands hundreds tens tenths hundredths thousandths millionths billionths

6. 2 types of speed Your average speed is the calculated measure of your speed over a distance. v av = total distance/total time of trip Your instantaneous speed is your speed at any particular instant. Not affected by previous speed, time travelled.

7. Constant Speed If instantaneous speed remains the same over a period of time, we say it is travelling with constant speed. Cruise control At constant speed, the average speed is the same as the instantaneous speed.

8. Average Speed What is an average? v av= Δ d/ Δ t Δ = “change in” Δ d/ Δ t = “change in distance/ change in time”

9. Finding average speed d= 10m t= 2s v=? v=d/t v=10m/2s v=5m/s

10. Physics problems Write down what you know. Write down what you are looking for. Decide which equation to use.

11. Problem #1 Chris runs to school, a total distance of 4.5km. He has to slow down twice to cross busy streets, but overall the journey takes 0.62h. What is Chris’ average speed during the trip? Δ d= 4.5km Δ t= 0.62h V av = ? V av = Δ d/ Δ t V av = 4.5km 0.62h V av =7.3km/h

12. Problem #2 Jeff is trying to predict how much time is needed to ride his bike to the beach. He knows that the distance is 45km/h. He will have to slow down to climb hills but he knows he will average about 20km/h. How long should his trip take? Δ d= 45km V av = 20km/h Δ t= ? V av = Δ d/ Δ t Δ t= Δ d/v av Δ t= 45km 20km/h Δ t= 2.3h