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Newton's Laws Introduction Practice Tests

These Grade 8 Science practice tests cover Newton's First, Second, and Third Laws, inertia, balanced and unbalanced forces, net force, F = ma, acceleration, action-reaction pairs, force diagrams, and safety applications.

Skills covered

  • Explaining inertia and constant velocity with Newton's First Law
  • Using F = ma to connect force, mass, and acceleration
  • Identifying action-reaction pairs on different interacting objects
  • Reading force diagrams and calculating net force and acceleration
  • Applying Newton's Laws to vehicles, sports, rockets, walking, and safety equipment

How to use these practice tests

First identify the object being analyzed and draw the forces acting on it. Add the forces with direction, decide whether the net force is zero, and then apply the appropriate Newton law or F = ma relationship.

For more Grade 8 Science practice, return to the Grade 8 Science category.

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Grade 8 Newtons Laws Introduction Practice Tests

Practice Grade 8 Science questions about Newtons First, Second, and Third Laws, inertia, net force, acceleration, force pairs, diagrams, and applications.

Choose the best answer for each question. Identify the Newton law, track force directions and objects, and use F = ma when calculation is needed.

10 Questions
0/10 Questions0 %
Correct 0
Incorrect 0
Unanswered 10
1. QuestionMultiple choice

What should a free-body diagram include?

Please select an answer first.

Correct answer: A

The correct answer is Arrows for the external forces acting on one selected object.

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

A free-body diagram isolates one object and represents the forces acting on it.

2. QuestionMultiple choice

In which direction does kinetic friction act for a box sliding east?

Please select an answer first.

Correct answer: B

The correct answer is West, opposite the sliding direction.

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Kinetic friction opposes relative sliding motion.

3. QuestionMultiple choice

A box has 12 N right and 7 N left. What is its net force?

Please select an answer first.

Correct answer: C

The correct answer is 5 N right.

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Subtract the opposite forces: 12 N right minus 7 N left equals 5 N right.

4. QuestionMultiple choice

A 2 kg object experiences a net force of 8 N. What is its acceleration?

Please select an answer first.

Correct answer: D

The correct answer is 4 m/s².

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Use a = F / m: 8 N divided by 2 kg equals 4 m/s².

5. QuestionMultiple choice

A 3 kg object accelerates at 4 m/s². What net force acts on it?

Please select an answer first.

Correct answer: A

The correct answer is 12 N.

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Use F = ma: 3 kg multiplied by 4 m/s² equals 12 N.

6. QuestionMultiple choice

Why does an object have weight even when it is not moving?

Please select an answer first.

Correct answer: B

The correct answer is Gravity acts on its mass whether or not the object is accelerating..

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Weight is the gravitational force on mass and can be balanced by another force while the object remains at rest.

7. QuestionMultiple choice

An elevator moves upward at constant velocity. What is true about its net force?

Please select an answer first.

Correct answer: C

The correct answer is The net force is zero..

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Constant velocity means zero acceleration, so upward and downward forces balance.

8. QuestionMultiple choice

Which situation shows an action-reaction pair rather than two forces on one object?

Please select an answer first.

Correct answer: D

The correct answer is A swimmer pushes water backward and water pushes the swimmer forward..

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

The swimmer-water pair acts on two different interacting objects, which identifies a Third Law pair.

9. QuestionMultiple choice

Why do passengers lean backward when a bus accelerates forward?

Please select an answer first.

Correct answer: A

The correct answer is Their bodies resist the change from rest because of inertia..

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

The body tends to remain at rest while the bus moves forward beneath it.

10. QuestionMultiple choice

A sled moves at constant speed in a straight line. Which statement is correct?

Please select an answer first.

Correct answer: B

The correct answer is The net force on the sled is zero..

  1. Identify the law or force: Decide whether the situation demonstrates inertia, the force-mass-acceleration relationship, or an action-reaction pair.
  2. Track the objects and directions: List the forces, identify which object receives each force, and determine the net force and direction when needed.
  3. Apply the equation or model: Use F = ma, a force diagram, data, or a real-world example to check that the explanation matches Newton law.

Constant velocity means no acceleration and therefore zero net force, even though individual forces may act.

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