You are right. I should have said Kinetic Energy.
Momentum is conserved.

(1/2)mass times the velocity squared is equal to the force times the distance it takes to stop the flying objects in your vehicle.
(force X distance) = (mass X velocity^2)/2

This gives you the force as Footpounds and the squaring of the effect due to doubling the speed holds true.
If you get in an accident at twice the speed that bobble head dog in your rear window will go 4 inches into your skull instead of just 2 inches.
Traveling three times as fast it takes 9 inches to stop as it passes through your skull.

I just am really bad at remembering formulas that I seldom use.

However, I have made checking for loose objects a standard procedure whenever I get into any vehicle now.
Right up there with all the other standard checks.