# Why does glass break at a given momentum?

My question is:Why is it more accurate to suppose that a sheet of glass will break, after being hit by a projectile with a given momentum, than suppose that it will break after receiving an impact force of f, or an impact energy of E

https://www.youtube.com/watch?v=OjvCNDF4RYw I watched this video and tried to solve the problem, i once found the equation in an excel spreadsheet but i cant found the spreadsheet.

In the equation i calculated at what momentum does the sheet break.

What surprised me is that glass generally breaks at a given momentum, not at a given force or impact energy. The error of nasanerd was calculating energy. I once did a experiment with a tiny glass plate, i put about 3 kg on it and pushed my finger with little force on the weight and it broke only after i did it, then i put about 7 kg slowly and it broke only when i pushed the weight with my finger, of course if i put 50 kg force on the glass it will break.

• Aside, but confusing: How does this video disprove 9/11? – Jahan Claes Jun 26 at 0:12
• the title is wrong, it has nothing to do with 9/11 – Sartem Cacartem Jun 26 at 0:50
• isn't force defined as dp/dt, . iis not that what is happening when momentum is transferred to glass? (I am not the one downvoting) – anna v Jun 26 at 5:50

The rate of change of momentum itself is the force $$dp/dt$$When you place the block on the glass sheet, the impulse generated is not enough to break the glass, because maybe you're placing it too carefully. Thus when you push and give some momentum to the block the glass breaks. What you need to look at is the breaking strength of the glass and the amount of energy you're transferring to the glass sheet per unit time.