Same impulse, different mass. Same mass, different shape. Physics has two surprises here.
What you're seeing
Left — two boxes with different masses.
Apply the same impulse. Watch which one goes higher.
Right — a cube and a tall rod with the
exact same mass.
Apply the same spin. Watch which one spins faster.
Experiment 1 — Linear Mass
Box A vs Box B
Same impulse hits both boxes. Lighter box gets more velocity.
Experiment 2 — Rotational Inertia
Cube vs Rod — same mass, different shape
Both are 3 kg.
The rod's mass is spread far from its center axis —
like a figure skater with arms stretched out.
Same spin impulse, very different result.
Key Takeaways
🏋️ Heavier = harder to accelerate
Same impulse → lighter box goes faster.
Δv = impulse / mass — double the mass, half the velocity change.
🍎 Gravity ignores mass (Galileo)
Drop both boxes. They land together — every time.
The engine applies F = m × g then divides by mass to get
acceleration. Mass cancels. Fall speed is always g.
🌀 Shape affects spin resistance
Same mass, different spin speed. The rod's mass sits far from its
center — high rotational inertia. Arms-out skater spins slowly;
arms-in skater spins fast. Mass × distance² determines resistance to spin.