NAME_** Answers**___ DATE___

PERIOD____ MOTION I

Ideas: Speed is a rate, a ratio of change in position

Speed = Change in Distance divided by Change in Time

S=D/T is the same as Speed is time into distance.

Average Speed is Total Change in Distance divided by Change in Time

Velocity is Speed with a direction (+ is one way, - the other way)

Acceleration is Change in Velocity divided by Change in Time.

On a distance time graph, slope is velocity. On a speed time graph, slope is acceleration.

1. Use the data in this table to draw three distance time graphs on a piece of graph paper. Mark time units along the bottom and mark distance units along the side of the paper. Use a different color pen or kind of line for each car.

(seconds) CAR A CAR B CAR C

1 4 1 2

2 8 3 4

3 12 8 6

4 16 10 8

5 20 16 10

6 24 22 12

7 28 24 14

8 32 26 16

Now, answer these questions:

2. Which line has the steepest slope? What does this tell you about the speed of the car?

3. Which car did not travel at a constant speed? How do you know? How does a line showing constant speed compare with a line showing changing speed?

4. What is the average speed of each car?

Car B has an average speed of Vavg=D/T = 26 m/8 s = 3.25 m/s

Car C has an average speed of Vavg=D/T = 16 m/8 s = 2 m/s

6. Explain why it would be impossible to see a distance-time graph with a straight up and down line (vertical slope):

It is also impossible for the line to to the left… meaning going backwards in time!

7. A car goes 30 kilometers in the first 30 minutes of a trip and then 50 more kilometers in the next 30 minutes. Find the car's average speed for the trip.

Total time is 30 min + 30 min = 60 min

Vavg=D/T = 80 km/ 60 min = 1.333 km/min or 80 km/hr !

8. A Car starts out on a trip down a long straight road. As it travels, it can move at a steady speed, speed up, slow down, or even stop. The distance time-graph for the car's trip is shown. Using the graph, describe the changes in motion that occurred during the car's trip.

stopped, then goes quickly steadily forward, then

goes at a constant speed backwards…

9. Shown in this picture are distance-time lines for two ships during part of their voyage. Which ship has the greater speed at time = 2 hours? How can you tell?

Greater distance in the same time…

9.5 Over the time up to time = 5 hours, how do the average speeds of the two ships compare?

10. LOOK AT THE GRAPH. THEN ANSWER THE QUESTIONS:

10.1 In the first hour of the hike, what is the hikers speed?

a) 1 km/hr

10.2 What is the hiker's average speed during the first two hours of the hike?

a) 2 km/hr b) 2.5 km/hr

10.3 What is the hiker's speed for the entire hike?

a) 1 km/hr

11 Match the correct distance-time graph with the car it represents

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12 Draw a rough idea of what a distance-time graph would look like for an object that: starts off away from the starting line, goes steadily backwards for awhile, then stays perfectly still, then goes slowly steadily forward, then goes quickly steadily forward, then accelerates forward, then travels backwards to the starting line:

Match each description with the correct graph and table:

1) A car stationary at point P GRAPH __

2) A car stationary at a distance away from point P GRAPH ___

3) A car moving away from point P at constant speed GRAPH ___

4) A car slowing down and moving away from P GRAPH ___

6) A car moving towards P at a constant speed GRAPH ___

7) A car slowing down as it approaches P GRAPH ___

8) A vehicle increasing in speed as it approaches P GRAPH ___