What kind of magnets will attract

Can somebody explain to me how newton's 3rd law relates to momentum? ~ap physics 1

Zeros that follow non-zeros numbers and are also to the right of a decimal point are significant

Estimate the schwarzschild radius (in kilometers) for a mini-black hole formed when a superadvanced civilization decides to punish you (unfairly) by squeezing you until you become so small that you disappear inside your own event horizon. (assume that the your weight is 50 kg)