Constant Versus Average Speed

Ant #1 crawled 12 inches in 1 second.

Ant #2 crawled 24 inches in 1 second.

Compare the speed of the ants- which one

is faster? How does the distance compare?

DIRECTLY PROPORTIONAL TO DISTANCE

Greater speed (faster)= more distanceLess speed (slower) = less distance

The top plane flew 220 meters in 1 second.

A bottom plane flew 220 meters in 2 seconds.

Compare their speeds-which plane

is faster? How do the times compare?

SPEED IS….

Inversely Proportional to TIME

Greater speed, less time

Less speed, more time

CONSTANT SPEED

SPEED THAT DOES NOT

CHANGE

CONSTANT SPEED

AVERAGE SPEED

AVERAGE = total distance traveled

SPEED total time

AVERAGE SPEED

AVERAGE SPEED

A car travels 32 km during the first 2 hours. Then it travels 13 km in the next hour. What is the average speed of the car?

ANSWER: Avg speed= total distance/total time

total distance = 32 km + 13 km = 45 km

total time = 2 h + 1h = 3 hr

Avg speed = 45 km/3 hr

Avg speed = 15 km/hr

CONSTANT SPEED

Definitions:

A change in position in a certain amount of time is __________.

__________________ is the rate at which an object moves and is determined by dividing ____________ by _____________.

_________________________ is speed that does not change.

_________________________ is calculated by dividing the total distance by the total time.

SPEED WORKSHEET

Complete for homework

Ken goes for a walk

0123456789

10

20 40 60 80 100 120

Time (minutes)

Dis

tan

ce (

km)

1.Calculate the speed at each point on the y-axis

Time (min)

20 40 60 80 100 120

Distance (km)

Speed (km/min

)

2. Describe the motion shown in the graph:

3.Calculate the average speed for the graph – how does this value compare to your calculations above?

3. How far would Ken travel if he walked for another hour (60 minutes)?

Ken goes for a walk

0123456789

10

20 40 60 80 100 120

Time (minutes)

Dis

tan

ce (

km)

1.Calculate the speed at each point on the y-axis

Time (min)

20 40 60 80 100 120

Distance (km)

1.5 3 4.5 6 7.5 9

Speed (km/min)

0.075 0.075 0.075 0.075 0.075 0.075

2. Describe the motion shown in the graph:

3.Calculate the average speed for the graph – how does this value compare to your calculations above? 0.075 km/min

3. How far would Ken travel if he walked for another hour (60 minutes)? 13.5 km

Michelle Goes on a Bike Ride

010

2030

4050

6070

80

1 2 3 4 5 6

Time (hours)

Dis

tan

ce (

km)

5.Describe the motion shown in the graph

6.How many different rates are shown? Label them using A, B, . . . . .

Time (hours)

A B C D

Distance (km)

Speed (min/km)8. What is the average speed for the entire trip? How does the value compare to your calculations above?

9. Can you predict how far Michelle will travel if she travels for another 2 hours? Why or why not? What additional information do you need?

7. Calculate the speeds for the different segments of the journey (Hint - you will have to use change in distance!)

Michelle Goes on a Bike Ride

010

2030

4050

6070

80

1 2 3 4 5 6

Time (hours)

Dis

tan

ce (

km)

5.Describe the motion shown in the graph (moving at varying speed)

6.How many different rates are shown? Label them using A, B, . . . . .

Time (hours) A (1 h) B (1h) C (2 h) D (1h)

Distance (km) 10 0 40 10

Speed (km/h) 10 0 20 10

8. What is the average speed for the entire trip? How does the value compare to your calculations above? 11.7 or 12 km/h

9. Can you predict how far Michelle will travel if she travels for another 2 hours? Why or why not? What additional information do you need?

7. Calculate the speeds for the different segments of the journey (Hint - you will have to use change in distance!)