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8th grade · Science · Unit 8 of 16

Speed, Velocity & Motion Graphs

Average speed, speed versus velocity, and reading distance-time graphs.

What your child practices

Practices calculating average speed from distance and time, telling speed from velocity (which includes direction) and distance from displacement, and reading distance-time graphs.

Alabama Course of Study content standard: 8.9; 8.10 · speed, velocity and acceleration on motion graphs

How we explain it

Children can open this short lesson before they practice.

  1. Average speed = distance ÷ time.
  2. Velocity includes direction. Displacement is how far you end up from the start, with direction.
  3. On a distance-time graph, a steeper line is faster and a flat line means stopped.

Example: You walk 5 m east, then 3 m west. What is your displacement? You end up 5 − 3 = 2 m from the start. You are still east of the start. Answer: 2 m east

Speed, Velocity & Motion Graphs in Alabama

In the Alabama Course of Study, this is unit 8 of 16 in 8th grade Science, after Chemical Change and before Motion, Forces & Newton’s Laws.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alabama State Department of Education (ALSDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    On a distance-time graph, the slope of the line equals…

    • force
    • time
    • speed
    • mass

  2. Question 2

    A toy car rolls 6 m in 3 s. What is its average speed?

    • 18 m/s
    • 3 m/s
    • 2 m/s
    • 9 m/s

  3. Question 3

    A runner goes 400 m in 80 s. What is the average speed?

    • 5 m/s
    • 480 m/s
    • 320 m/s
    • 0.2 m/s

  4. Question 4

    Velocity is speed with…

    • a mass
    • a temperature
    • a direction
    • a color

  5. Question 5

    On a distance-time graph, a flat horizontal line means the object is…

    • moving at constant speed
    • moving backward fast
    • speeding up
    • not moving

  6. Question 6

    A bus travels 120 km in 1.5 hours. Its average speed is…

    • 180 km/h
    • 121.5 km/h
    • 80 km/h
    • 60 km/h

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