Constant Velocity Is the Default

You'll learnthat with zero net force an object keeps its velocity, motion needs no fuel.

A rocket with its engines off, an astronaut holding on to nothing, and the hardest instinct in physics to un-learn: the belief that motion has to be fed.

8 STEPS · 6 QUICK CHECKS · v5

INERTIA LAB

Before you start

What you're looking at

A rocket coasting through deep space at +20 m/s with engines off, and an astronaut floating beside it, touching nothing.

The question

If nothing pushes the astronaut, do they fall behind the coasting rocket?

Watch for

Predict what happens with no force acting, then check whether the gap between rocket and astronaut changes.

What the symbols mean

The velocity arrow shows steady +20 m/s; the ENGINES OFF chip marks zero net force, independent of velocity.

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