How do I describe and calculate the effect of an impacting object?

Question

My lab studies the physiology of impact injury on biological tissues. I use a pneumatic cylinder to impart injury into a biological sample and then assess the molecular and physiological changes in that tissue. It is the first step in trying to understand the pathophysiology of traumatic brain injury. So, I have the mass of the internal moving components of the cylinder (the rod and piston body = 25grams) and I have the velocity of these moving components (let's call it 10m/s). I also have the sample and cylinder set up so that the total displacement is 5mm. The sample sits on a foam pad. Some of this displacement is represented by compression of the sample, but for the most part the sample rapidly accelerates and decelerates through this 5mm displacement. Most of the related literature simply reports the velocity of the impact. However, I know enough physics to know that velocity is but one piece of the impact physics. So, my questions: 1. Colloquially, one might ask what is the force imparted on the tissue. But, that might not be the correct term. What is the best way to label the effect of the cylinder on the tissue? Is Force correct? Would it be Kinetic Energy? I'm just trying to figure out the most informative/accurate description of the effect of the cylinder on the tissue. 2. Then, how do I calculate that (what ever it is: force, KE, ...)?

Answer 1

Considering the subject you are studying, I would say force. I would not say kinetic energy because that is typically used for projectiles, The same would go for the term impact, which is the change in momentum when one object hits another.

Answer 2

Hi,

You might find the information on https://www.physicsclassroom.com/class/momentum/Lesson-1/Momentum-and-Impulse-Connection helpful when working with impulse/momentum interactions. It's very basic but provide a good feel for the problem.

Jim