Physics
Inertia and Newton's First Law
Quick fact
A space shuttle continues moving at high speed even after its engines shut off because there's almost no friction in space.
Why this is interesting
Have you ever noticed that a ball keeps rolling until something stops it? That’s inertia in action—your everyday force of motion resistance.
Read the full explanation
Understanding Inertia and Newton's First Law
Imagine pushing a shopping cart. If you stop pushing, the cart will eventually slow down and stop due to friction. But if there were no friction, it would keep moving forever. That’s what Newton’s first law is all about: objects stay in motion unless something changes their state.
A deeper explanation
Newton's first law, also known as the law of inertia, states that an object will remain at rest or continue moving with constant velocity unless a net external force acts on it. Inertia is the property that resists such change. The more mass an object has, the greater its inertia—meaning it’s harder to start or stop its motion. This principle helps us understand why seatbelts are necessary in cars and how objects behave when forces are applied.