My cousin proposed this lab that requires me to create a pen and uses its springs to dispense a piece of paper that lay flat on a high surface to the ground. The pen looks like this: From this lab objective, I need to find the K constant of the spring inside the pen using Hooke's law F= -Kx. I was able to find the distance, time, and acceleration (d=1/2at^2) but still unable to figure out how to find the mass to complete my finding in applied force. This image is the only hint he's willing to give me, please help me find the mass or force of this experience?