Newton's Laws of Motion Quiz

Grade 8 · Science · Quiz

10 questions covering all three of Newton's laws, force calculations, and real-world applications.

Questions

1. Which of Newton's Laws is also known as the Law of Inertia?

   1. First Law
   2. Second Law
   3. Third Law
   4. Fourth Law
   Show answer

   Answer: First Law

   The First Law states objects resist changes in motion — this resistance is called inertia.

2. A 10 kg object has a net force of 50 N applied to it. What is its acceleration?

   1. 500 m/s²
   2. 5 m/s²
   3. 0.2 m/s²
   4. 60 m/s²
   Show answer

   Answer: 5 m/s²

   a = F/m = 50 N ÷ 10 kg = 5 m/s².

3. When a swimmer pushes off a pool wall, she moves forward. This is an example of:

   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

   She pushes the wall (action), and the wall pushes her forward (equal and opposite reaction).

4. Two objects, one with mass 2 kg and one with mass 6 kg, have the same force applied. Which accelerates faster?

   1. The 6 kg object
   2. The 2 kg object
   3. They accelerate equally
   4. Cannot be determined
   Show answer

   Answer: The 2 kg object

   From F = ma, a = F/m. Smaller mass means greater acceleration for the same force.

5. An object moving at constant velocity has a net force of zero acting on it.

   Show answer

   Constant velocity means no acceleration, so by F = ma, net force must be zero.

6. A book sits on a table. The book's weight pushes down on the table. According to Newton's Third Law, what is the reaction force?

   1. Gravity pulling the book down
   2. The table pushing up on the book with equal force
   3. Friction between the book and table
   4. The air pressure on top of the book
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   Answer: The table pushing up on the book with equal force

   The normal force from the table is the reaction to the book's weight pressing on the table.

7. The SI unit of force is the ___.

   Show answer

   Force is measured in Newtons (N), named after Isaac Newton.

8. A car traveling at 60 mph comes to a sudden stop. Passengers lurch forward. Which law explains this?

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

   Passengers were in motion and tend to stay in motion (inertia) when the car stops.

9. What happens to acceleration if you double the force while keeping mass constant?

   1. Acceleration doubles
   2. Acceleration halves
   3. Acceleration stays the same
   4. Acceleration quadruples
   Show answer

   Answer: Acceleration doubles

   From a = F/m, doubling F with constant m doubles a.

10. Action and reaction forces in Newton's Third Law act on the same object.

    Show answer

    Action-reaction pairs always act on different objects. The action is on one object; the reaction is on the other.

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