Interaction Pairs & Force Diagrams — Drills · Grade 8 Science
Chapter: ForcesWhat these drills covers
By the end of Interaction Pairs & Force Diagrams you should be able to:
- I can label each force’s source and receiver and keep interaction partners on separate diagrams.
- I can find a one-dimensional net force and distinguish it from velocity.
4 questions, written answer, each with a worked explanation.
Vocabulary used: interaction, force diagram, receiver, normal force, net force, model, evidence, system boundary, assumption.
Problem 1
Answer and explanation
The cart. Forces exerted on the table or on Earth belong in separate diagrams, even though they are connected interactions.
The cart. Forces exerted on the table or on Earth belong in separate diagrams, even though they are connected interactions.
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
Answer and explanation
Only one acts on the cart. Adding a force on the person to the forces on the cart mixes receivers and gives an invalid net force.
Only one acts on the cart. Adding a force on the person to the forces on the cart mixes receivers and gives an invalid net force.
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
Answer and explanation
No. Horizontal and vertical comparisons are separate in this simple model. The vertical forces may balance while horizontal motion changes.
No. Horizontal and vertical comparisons are separate in this simple model. The vertical forces may balance while horizontal motion changes.
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
Answer and explanation
No. It can be slowing under a leftward net force or moving steadily with zero net force. Motion direction and net-force direction are different quantities.
No. It can be slowing under a leftward net force or moving steadily with zero net force. Motion direction and net-force direction are different quantities.
Response criteria
- Use the supplied conditions and relevant evidence.
- Explain the scientific mechanism or calculation.
- State a meaningful limitation or testable next step.