Forces and Newton's Laws of Motion Quiz

Grade 10 · Science · Quiz

Test your understanding of Newton's three laws, force calculations, and real-world applications of classical mechanics.

Questions

1. A 5 kg box is pushed with a net force of 20 N. What is its acceleration?

   1. 4 m/s²
   2. 100 m/s²
   3. 0.25 m/s²
   4. 25 m/s²
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   Answer: 4 m/s²

   F = ma → a = F/m = 20 N ÷ 5 kg = 4 m/s².

2. Inertia is greatest in objects with the least mass.

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   Answer: False

   Inertia is directly proportional to mass — greater mass means greater inertia (more resistance to changes in motion).

3. A swimmer pushes off the pool wall and moves forward. This demonstrates:

   1. Newton's First Law
   2. Newton's Second Law
   3. Newton's Third Law
   4. The law of gravity
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   Answer: Newton's Third Law

   The swimmer exerts a backward force on the wall (action); the wall exerts an equal and opposite forward force on the swimmer (reaction) — propelling them forward.

4. When the net force on an object is zero, the object is in ___.

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   Answer: equilibrium

   Equilibrium means net force = 0, so acceleration = 0. The object is either at rest or moving at constant velocity.

5. Which of the following is NOT a contact force?

   1. Friction
   2. Normal force
   3. Tension
   4. Gravity
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   Answer: Gravity

   Gravity is a non-contact (action-at-a-distance) force — it acts between masses without physical contact. Friction, normal force, and tension all require contact.

6. According to Newton's Second Law, doubling the mass of an object while keeping force constant will double its acceleration.

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   Answer: False

   From F = ma: a = F/m. Doubling mass while keeping force constant halves the acceleration, not doubles it.

7. A 2 kg object accelerates at 5 m/s². What is the net force acting on it?

   1. 2.5 N
   2. 7 N
   3. 10 N
   4. 0.4 N
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   Answer: 10 N

   F = ma = 2 kg × 5 m/s² = 10 N.

8. The tendency of an object to resist changes in motion is called ___.

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   Answer: inertia

   Inertia is the property of matter that resists changes in velocity. It is described by Newton's First Law and is proportional to mass.

9. Action-reaction force pairs in Newton's Third Law act on the same object.

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   Answer: False

   Newton's Third Law action-reaction pairs ALWAYS act on different objects. If A pushes B (action), B pushes A back (reaction) — two objects, two forces.

10. A book sits on a table. The weight of the book is 20 N. What is the magnitude of the normal force from the table?

    1. 0 N
    2. 10 N
    3. 20 N
    4. 40 N
    Show answer

    Answer: 20 N

    For a book at rest on a table, the net force is zero. The normal force from the table must exactly equal the book's weight (20 N) in the opposite direction.

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