"At 60 it will have 4 times the momentum it did at thirty and will do 4x the damage instead of 2x.
(force = mass X velocity^2)"

Formulas and definitions not quite right, but point well taken.

Force = mass x acceleration(not the same as velocity squared)

Momentum = mass x velocity

Energy = 1/2mass x velocity squared

At 60, it will only have double the momentum.

Damage is a bit relative. Ballisticians have argued for decades about what is an appropriate calculation for approximating damage from a projectile. I prefer the force calculation, mainly because it is the only formula that deals specifically with terminal ballistics, although it too is an incomplete calculation.


The bottom line is getting hit in the head with a clipboard at 30 mph is not generally as devastating as one at 60 mph, and both situations should, and can be, avoided taking the recommended precautions.