Collisions, Deformation & Changes in Motion — Drills · Grade 8 Science

Chapter: Motion

What these drills covers

By the end of Collisions, Deformation & Changes in Motion you should be able to:

4 questions, written answer, each with a worked explanation.

Vocabulary used: collision, deformation, elastic deformation, permanent deformation, peak force, model, evidence, system boundary, assumption.

Problem 1

Why is an afterward photograph insufficient to detect temporary deformation?
Answer and explanation

An object can deform during contact and then recover. The after-image does not show the complete time sequence.

An object can deform during contact and then recover. The after-image does not show the complete time sequence.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 2

Does greater acceleration of the lighter cart imply a larger collision force on it?
Answer and explanation

No. Equal interaction forces can cause different acceleration because masses differ, and net-force calculations must account for other forces.

No. Equal interaction forces can cause different acceleration because masses differ, and net-force calculations must account for other forces.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 3

Can speed alone predict every dent?
Answer and explanation

No. It influences motion energy, but material response, geometry and how the object stops also affect damage.

No. It influences motion energy, but material response, geometry and how the object stops also affect damage.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

Problem 4

What do these peak records support?
Answer and explanation

Lower measured peak force for this padded setup under the stated matched conditions. They do not certify every pad or establish identical average forces or injury protection.

Lower measured peak force for this padded setup under the stated matched conditions. They do not certify every pad or establish identical average forces or injury protection.

Response criteria

  • Use the supplied conditions and relevant evidence.
  • Explain the scientific mechanism or calculation.
  • State a meaningful limitation or testable next step.

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