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Grade 8 · unit review

Review: Motion, Momentum and Collisions

Extend force learning with motion graphs and momentum accounting.

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Bring the unit skills together

Use these 4 new cases to check your reasoning. Choices are temporary and are not saved to an account, sent to staff or recorded as school grades. Download your current review choices before leaving or reloading.

Unit review questions
1. Supplied case 5: total distance (m)=60; elapsed time (s)=12, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows?
Need a hint?
  • Average speed equals distance in meters divided by time in seconds.
  • Time belongs in the denominator.
2. Supplied case 5: mass (kg)=6; signed velocity (m/s)=2, using the explicitly named quantities. Momentum equals mass in kilograms multiplied by signed velocity in meters per second. What result follows?
Need a hint?
  • Momentum equals mass in kilograms multiplied by signed velocity in meters per second.
  • Momentum is not kinetic energy.
3. Supplied case 5: first signed momentum (kg·m/s)=15; second signed momentum (kg·m/s)=-7, using the explicitly named quantities. Total momentum equals the two signed supplied momenta added. What result follows?
Need a hint?
  • Total momentum equals the two signed supplied momenta added.
  • State the isolated-system assumption for conservation.
4. Which scientific label fits the specifically described step or feature? Supplied case: Position increases at constant rate.
Need a hint?
  • Look for the described feature: position increases with time.
  • Compare the given mechanism with the other labels; do not infer unmentioned events.

The download contains your current choices and any checked feedback. Keep the separate transfer-task work in your own document; downloading its instructions does not mark it complete.

Use the skills in a new task

Create a four-panel explanation for “Motion, Momentum and Collisions” using one supplied case from each lesson. Include the observation, scientific mechanism or calculation, result and a limitation. You may draw and speak your explanation; all inputs are supplied.

Work on paper or in your own document. Explain the choices you made.

  • Use one supplied case from each of the four lessons.
  • Name the relevant structure, quantity or process in every panel.
  • Show calculations with units or a causal evidence chain.
  • Distinguish source facts from fictional classroom data.
  • State a model limit or a condition that would change the result.
Compare with a model response

Panel 1: Supplied case 1: total distance (m)=24; elapsed time (s)=6, using the explicitly named quantities. Average speed equals distance in meters divided by time in seconds. What result follows? Result: 4 m/s. Reasoning: Substitute the supplied values: (24)/(6) = 4 m/s. Use total distance for speed. Average speed need not equal every moment’s speed. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 2: Supplied case 1: mass (kg)=2; signed velocity (m/s)=3, using the explicitly named quantities. Momentum equals mass in kilograms multiplied by signed velocity in meters per second. What result follows? Result: 6 kg·m/s. Reasoning: Substitute the supplied values: (2)*(3) = 6 kg·m/s. Include velocity direction through its sign. Mass does not become negative when motion reverses. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 3: Supplied case 1: first signed momentum (kg·m/s)=6; second signed momentum (kg·m/s)=-2, using the explicitly named quantities. Total momentum equals the two signed supplied momenta added. What result follows? Result: 4 kg·m/s. Reasoning: Substitute the supplied values: (6)+(-2) = 4 kg·m/s. Add signed momenta. Opposite signs can partly cancel. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified. Panel 4: A position-time segment rises from 2 m to 10 m over 4 s. What follows? Which inference or prediction is best supported? Result: Its average velocity is(10−2)/4=2 m/s.. Reasoning: Slope is position change divided by elapsed time; a straight slope does not imply acceleration. Model limitation: only the stated classroom boundary and supplied observations are established; unmeasured real-world performance remains unverified.

A different response can also meet the criteria. Compare the evidence and reasoning, rather than copying the wording.