Let me preface this by saying I am not a physics expert, but this is something I was wondering and I would love a technical explanation.
For example, say you're walking with an filled plastic grocery bag and you can tell that the handle might rip just due to the pressure between your fingers and the handles being great. However, it does not rip and you are making it… UNTIL—you decide to raise your hand holding the bag and place it onto the counter when you get home, and as you do so, the bag rips.
If no additional weight was placed upon the bag, just the movement of raising your hand, what causes the bag to experience a greater force that caused it to break?
Please feel free to explain in a technical manner but assume descriptions would be helpful!