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Science · Grades 8–11

Motion graphs and force reasoning

Speed is the magnitude of velocity. Acceleration is a change in velocity per unit time.

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Understand the idea

Velocity is directional

Speed is the magnitude of velocity. Acceleration is a change in velocity per unit time.

Net force matters

Zero net force means zero acceleration in an inertial frame, not necessarily zero velocity.

Examples and reasoning

A position–time graph is a straight line with positive slope. The object has

constant positive velocity

constant positive velocity

A horizontal position–time graph represents

constant position

constant position

Check your understanding

  1. The slope of a velocity–time graph gives

    1. mass
    2. force without knowing mass
    3. acceleration
    4. position directly

  2. The signed area under a velocity–time graph gives

    1. mass
    2. instantaneous acceleration
    3. density
    4. displacement

  3. A car turns at constant speed. Can it have acceleration?

    1. Only if its colour changes.
    2. Only when parked.
    3. No, because speed is constant.
    4. Yes, because its velocity direction changes.

  4. Velocity changes from 3 m/s to 15 m/s in 4 s. A learner divides 15 by 4 for acceleration. Explain the missing step.

Answers and marking notes

Answers and marking notes
  1. acceleration

    acceleration

  2. displacement

    displacement

  3. Yes, because its velocity direction changes.

    Yes, because its velocity direction changes.

  4. Use the change in velocity, not the final velocity alone: (15 − 3)/4 = 3 m/s².

    Use the change in velocity, not the final velocity alone: (15 − 3)/4 = 3 m/s².

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Learning preview · teacher review required. Grade bands are approximate, not official curriculum alignment.