Newton's 3rd Law

Every force has an equal and opposite reaction force — acting on a different object

Newton's 3rd Law — Rocket
The rocket pushes exhaust gases DOWN. The exhaust pushes the rocket UP with an equal force.
Set thrust and press Launch. Both force arrows will always be exactly the same length.
T = 0 N
Thrust 120 N
Fuel
Full
Newton's 3rd Law
Set the masses with the sliders then press Launch.
Force on A from B = Force on B from A — always equal, always opposite
F = 0 N
Mass A 2.0 kg
Mass B 2.0 kg