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Quiz: Forces and Newton's Laws

Test your understanding of forces and newton's laws with these 10 questions.

1. What is the SI unit of force?

  1. Joule
  2. Newton
  3. Pascal
  4. Watt
Show Answer

The correct answer is B. The SI unit of force is the Newton (N), named after Sir Isaac Newton. One Newton is the force required to accelerate a 1 kg object at 1 m/s². Joule is a unit of energy, Pascal is a unit of pressure, and Watt is a unit of power.

Concept Tested: Force

See: Chapter 4 - Forces and Newton's Laws

2. Two forces of 5 N and 3 N act on an object in the same direction. What is the net force?

  1. 2 N
  2. 8 N
  3. 15 N
  4. 5 N
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The correct answer is B. When forces act in the same direction, we add them together. Net force = 5 N + 3 N = 8 N. This is vector addition for parallel forces.

Concept Tested: Net Force

See: Chapter 4 - Forces and Newton's Laws

3. Which statement best describes Newton's First Law of Motion?

  1. Force equals mass times acceleration
  2. For every action, there is an equal and opposite reaction
  3. An object at rest stays at rest unless acted upon by a net force
  4. Energy is always conserved in a system
Show Answer

The correct answer is C. Newton's First Law states that an object at rest stays at rest and an object in motion stays in motion with constant velocity unless acted upon by a net force. This describes inertia and is the foundation of understanding motion.

Concept Tested: Newton's First Law

See: Chapter 4 - Forces and Newton's Laws

4. A 2 kg object accelerates at 3 m/s² when a net force is applied. What is the magnitude of the net force?

  1. 0.67 N
  2. 1.5 N
  3. 6 N
  4. 5 N
Show Answer

The correct answer is C. Newton's Second Law states F = ma. Using the given values: F = 2 kg × 3 m/s² = 6 N. This is the fundamental relationship between force, mass, and acceleration.

Concept Tested: Newton's Second Law

See: Chapter 4 - Forces and Newton's Laws

5. If a hand pushes on a wall with a force of 50 N, what force does the wall exert on the hand?

  1. 0 N (the wall is stationary)
  2. 25 N (half the applied force)
  3. 50 N in the opposite direction
  4. 100 N in the opposite direction
Show Answer

The correct answer is C. Newton's Third Law states that for every action, there is an equal and opposite reaction. The wall pushes back on the hand with exactly 50 N in the opposite direction. This is why your hand feels pressure when you push against a wall.

Concept Tested: Newton's Third Law

See: Chapter 4 - Forces and Newton's Laws

6. A book rests on a table. The weight of the book is balanced by which force?

  1. Applied force
  2. Friction force
  3. Normal force
  4. Air resistance
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The correct answer is C. The normal force is the contact force perpendicular to a surface. When a book rests on a table, the normal force from the table surface balances the weight (gravitational force) of the book, keeping it in equilibrium.

Concept Tested: Normal Force

See: Chapter 4 - Forces and Newton's Laws

7. A 5 kg object rests on a horizontal surface on Earth. What is its weight? (Use g = 10 m/s²)

  1. 0.5 N
  2. 5 N
  3. 50 N
  4. 500 N
Show Answer

The correct answer is C. Weight is the gravitational force on an object: W = mg. For a 5 kg object: W = 5 kg × 10 m/s² = 50 N. Weight depends on both the object's mass and the strength of the gravitational field.

Concept Tested: Weight

See: Chapter 4 - Forces and Newton's Laws

8. How does static equilibrium differ from dynamic equilibrium?

  1. Static equilibrium occurs only in space; dynamic equilibrium occurs on Earth
  2. Static equilibrium means the object is at rest; dynamic equilibrium means the object moves with constant velocity
  3. They are exactly the same and the terms are synonymous
  4. Dynamic equilibrium requires more forces than static equilibrium
Show Answer

The correct answer is B. Static equilibrium occurs when an object is at rest with zero net force. Dynamic equilibrium occurs when an object moves with constant velocity (zero acceleration) with zero net force. Both involve net force = 0, but they describe different motion states.

Concept Tested: Equilibrium

See: Chapter 4 - Forces and Newton's Laws

9. A car accelerates forward. According to Newton's Third Law, this happens because:

  1. The engine pushes the car forward harder than friction resists
  2. The wheels push backward on the road, and the road pushes forward on the wheels
  3. The car's inertia is overcome by the engine's force
  4. The gravitational force on the car decreases
Show Answer

The correct answer is B. Newton's Third Law explains that action-reaction pairs always occur. When wheels push backward on the road, the road simultaneously pushes forward on the wheels. This forward push from the road is what accelerates the car forward.

Concept Tested: Action-Reaction Pairs

See: Chapter 4 - Forces and Newton's Laws

10. Which of the following scenarios describes an object in equilibrium?

  1. A ball falling toward Earth under gravity
  2. An airplane flying at constant speed and altitude
  3. A book sliding across a frictionless surface
  4. A rocket accelerating upward from Earth
Show Answer

The correct answer is B. Equilibrium requires zero net force and zero acceleration. An airplane flying at constant speed and altitude has zero net force (thrust balances drag, lift balances weight), so it is in dynamic equilibrium. The falling ball, sliding book, and accelerating rocket are all accelerating.

Concept Tested: Dynamic Equilibrium

See: Chapter 4 - Forces and Newton's Laws