Inertia Definition and Examples: A Physics Guide

📚 Quick Study Guide

• 🍎 Inertia is the tendency of an object to resist changes in its state of motion.
• 🚗 An object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a force. This is also known as Newton's First Law of Motion.
• ⚖️ Inertia is directly proportional to mass. The greater the mass, the greater the inertia.
• 📐 Mathematically, inertia is reflected in Newton's First Law. $\sum F = 0$ implies $a = 0$, meaning no acceleration (change in velocity) occurs without an external force.
• 🌎 Examples include: A soccer ball staying still until kicked, a car continuing to move after the brakes are applied, and a person continuing to move forward in a car that suddenly stops.

🧪 Practice Quiz

1. What is inertia?
   1. A force that causes acceleration.
   2. The tendency of an object to resist changes in its state of motion.
   3. The speed of an object.
   4. The energy of an object.
2. Which of Newton's Laws is most closely related to inertia?
   1. Newton's Second Law of Motion.
   2. Newton's Third Law of Motion.
   3. Newton's Law of Universal Gravitation.
   4. Newton's First Law of Motion.
3. How is inertia related to mass?
   1. Inertia is inversely proportional to mass.
   2. Inertia is directly proportional to mass.
   3. Inertia is not related to mass.
   4. Inertia is equal to the square root of mass.
4. A soccer ball is sitting at rest on the field. What best explains why it stays at rest?
   1. Gravity is the only force acting on it.
   2. Inertia keeps it at rest.
   3. Friction is the only force acting on it.
   4. The ball has no mass.
5. A car is moving at a constant speed. What happens when the brakes are applied?
   1. The car immediately stops due to inertia.
   2. The car continues to move forward due to inertia.
   3. The car accelerates.
   4. The car disappears.
6. If an object has a large mass, what can you conclude about its inertia?
   1. It has a small inertia.
   2. It has a large inertia.
   3. It has no inertia.
   4. Inertia is unrelated to mass.
7. Which of the following scenarios best demonstrates inertia?
   1. A rocket launching into space.
   2. A bird flying through the air.
   3. A person continuing to move forward when a car suddenly stops.
   4. A ball rolling downhill.