I'm extremely excited to embark on my physics project and it has all to do with ripping toilet paper rolls. As it is commonly known, when a full toilet paper roll is given a fast jerk, a sheet breaks off. However, as the roll is gradually used up, a faster jerk has to be applied or the toilet paper will unravel like crazy haha. Anyway, I'm interested in finding a relationship between the velocity at which the toilet paper roll has to be tugged and the radius of the roll ( as in how much it is used up). Now, i have to come up with the physics behind this: sum torque = (radius of roll) x ( Force of pull) - (distance from center to the core of the toilet roll) x ( Friction) and this is also equals to sum torque = (moment of inertia of roll) x ( angular acceleration) This is where i'm stuck at, i don't know about the physics that explains whether the roll will break or continue unraveling. Here are some thoughts, but they are most probably faulty: To simplify the problem, i've decided to consider an inertial ball ( ball hangs from a string, and another string hangs from the ball) at the lower string F = (change in momentum) / time thus if given a fast jerk F > (F required to break string) and therefore lower string breaks but why doesn't the upper string bring? is it because according to F = ma, the mass is so much greater than the string that it doesn't accelerate much? Please show me the physics behind why when a slow pull is applied, the upper string breaks while the lower string breaks if given a fast jerk. I think once i've understand this, i can apply my knowledge to ripping toilet paper. Thanks, i'll add more of my thoughts on this later when i come up with more ideas.