Untitled Flashcards SetC

🚨 Newton’s First Law of Motion – The Law of Inertia

🔑 Official definition (the textbook one):

🧠 What it REALLY means:

If you leave something alone, it keeps doing what it’s already doing —
Unless something interferes.

That’s it.
This law says: "Objects are lazy. They don’t change by themselves."

💬 Real-Life Examples (So you FEEL it):

✅ Object at rest stays at rest:

• A book on your table won’t fly off on its own.

• A ball won’t roll until you push it.

✅ Object in motion stays in motion:

• Kick a ball on ice — it keeps sliding for a long time. Why? There's little friction to stop it.

• A train keeps moving even after the engine stops. Why? It has inertia (and it takes time and force to stop it).

💣 Key Word: Inertia

Inertia = the tendency of an object to resist change in its motion.

• More mass = more inertia.
  ➤ A truck is harder to push than a bicycle.

• Less mass = less inertia.
  ➤ A feather moves easily because it has little inertia.

🧩 Breaking Down the Law

1. If there’s no net force, then:

• A still object stays still.

• A moving object keeps moving in a straight line at constant speed.

2. Only net force changes motion.

• Push it, pull it, friction, gravity, etc. = these change its motion.

💡 Common Mistake:

People think things stop because “that’s natural.”
Wrong. Things stop because of forces (like friction or air resistance).
If you removed all friction, motion would never stop. That’s the true world Newton imagined.

🔁 Summary (So You Never Forget):

🧠 Masterline (Your brain tattoo):