— ## What is Newton’s First Law? Newton’s First Law states: “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 an unbalanced force.” Let’s break that down: * “An object at rest stays at rest”: If something isn’t moving, it won’t start moving unless a force pushes or pulls it. * “An object in motion stays in motion with the same speed and in the same direction”: If something is already moving, it will keep moving at the exact same speed and in the exact same straight line forever, unless something stops it or changes its path. * “Unless acted upon by an unbalanced force”: This is the key! A force is “unbalanced” if it’s not canceled out by other forces. Only an unbalanced (or “net”) force can cause a change in an object’s velocity (i.e., cause it to accelerate). — ## Inertia The property of an object to resist changes in its state of motion is called inertia. * Mass and Inertia: The more mass an object has, the more inertia it has. A heavy truck has more inertia than a bicycle, meaning it’s harder to get the truck moving and harder to stop it once it’s going. — ## Interactive: Inertia in Action See how an object resists changes to its motion! <div class="animator-container"> <div style="margin-bottom: 0.8rem;"> </div> Newton's First Law: Inertia in Action An interactive simulation demonstrating inertia for objects at rest and in motion, with varying applied forces. Surface Object F Velocity: 0.0 m/s <div id="animationExplanation" class="animation-explanation" aria-live="polite"> <p>Observe how an object resists changes to its motion!

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Why Newton’s First Law Matters

  • Foundation of Dynamics: It’s the starting point for understanding how forces affect motion.
  • Understanding “Why Things Stop”: It helps us realize that objects don’t just stop because they “run out of force.” They stop because an unbalanced force (like friction or air resistance) acts on them.
  • Everyday Examples: Seatbelts in cars (your body’s inertia keeps it moving forward when the car stops), shaking a ketchup bottle (ketchup’s inertia keeps it moving when the bottle stops).

Audio Explanation

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💡 Quick Concept Check:

You're riding a skateboard and suddenly hit a curb. Why do you fly forward off the skateboard?

Click to Reveal Answer
You fly forward because of **inertia** (Newton's First Law). Your body was in motion with the skateboard, and when the skateboard suddenly stopped (due to the curb), your body's inertia caused it to continue moving forward until an unbalanced force (like hitting the ground) stopped you.

Ready to put your understanding of Newton’s First Law into practice? Check out these related skills:

Practice Problems

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