Help check my equation F=ma 2.27kg x .04 m/s/s =.908 newtons. I am doing a science project.?

Question

Help! I am 14 years old and I am doing a science project At What Velocity Does My Punch Have To Travel To Stop A Human Heart? I video recorded my punches and uploaded the video showing the duration of my punch from frames 50:19 to 50:23 -so .4secs. 50:21-50:23=.2sec. Using the formula F=ma 2.27kgsx.4m/s/s=.908newtons and 2.27kgsx2.2m/s/s=.54newtons. The 2.27kgs I turned pounds into kgs I looked up on the internet . My fist is about 5lbs. Please check if this is correct. If it is I would like to graph it. What graph should I use bar, linear. . Thamk you .

In response to the last answer - first of all thank you. As for acceleration, I analyzed the speed of my punch by frame rate and I saw I could punch up to .2 seconds from start of my punch to the full extension. I am not sure if this is the proper way to measure acceleration however I can see through frame rate analysis how fast I'm punching in seconds or part of a second. If it helps, I'm using Vegas Video for frame rate analysis.

Also, in what ways do you think I can graph this stuff. I can imagine bar and linear graphs but I really don't see a way that a pie graph fits this kind of project. -thank you again.

Answer 1

Thats a cool experiment you are doing. The method that you use to calculate the acceleration is not correct. What it sounds like you measured is simply how long it took for you to punch. Acceleration is a measure of how much your velocity changes in a given amount of time. For example if a car starts out going 0 mph then 5 mph then 10 mph then 15 mph...and so on his velocity is changing. But if he did all of that from 0-15 mph in 3 seconds his acceleration will be 5 mph every second . Just divide 15 by 3. What you did is simply take your time and say that that is your acceleration..which is equivalent to me saying the cars acceleration is 3 mph every second...which is incorrect. A way to get acceleration is to take the twice the distance your hand traveled and divide that by your time squared(.2 squared = .04). This number is very crude and probably inaccurate because it is a measure of your hand's acceleration if the acceleration is constant ( But it will get you closer to your goal than the numbers that you used) . Body mechanics is complicated thing when trying to analyze it but, you are on the right track.

P.S. That equation i told you about how to calculate acceleration looks like i just made it up, but its a real equation. Look up "constant acceleration" on yahoo search or something to get more info

Answer 2

How did you get the accerleration part? There's not enough infor on that.

If you are trying to calculate the force of your punch, you have to film it punching something and coming to rest.

You find the velocity of your punch through ur "frame method"....
You find the time taken from the point of contact to the point where your punch comes to rest.

Then you can apply the Newton's 2nd Law F=M(V-U)/t

However, you should try to attack the project using enery method. Find out how much energy is required to stop a human heart. Simply using the formula E=0.5mV^2

Hope that helps.