Okay, so I did some research and have found that the human skull is roughly 1/4" = 6.35mm thick. Helmet foam on the other hand is 20mm. So I think I can reasonably conclude that the time allowance afforded by the skull is 1/3 of the helmet foam. That is, if it's distance that is the operative...
I'm glad that the calculations appear to be in order, despite the baffling conclusion that 20km/h(w helmet)=2.8km/h(w.o helmet).
You're right about the force not being necessarily linear, but I think I just need something simple to illustrate the effectiveness of helmets.
While I can reliably...
Right, the wikipedia statement regards energy.
That aside, my calculations of force are sound? That with a helmet, hitting the the ground (or another object) at 20km/h, is roughly equivalent to hitting the ground at 2.8km/h without a helmet?
Yes. Is that not correct, given that we are reversing the direction?
Secondly, I have just drawn out a vector diagram to scale of the vectors in question. It seems to support #2, though I'm not sure how certain to be - given that I haven't work graphically with vectors in a while.
I don't think so, as can be seen here:
http://i543.photobucket.com/albums/gg464/yowatupguystill/vector-1.jpg
EDIT: I might have been correct on my first attempt, but I had assumed that this was correct: https://www.physicsforums.com/archive/index.php/t-275728.html
Homework Statement
I am required to find the change in velocity given these two vectors:
Va = 4.4 m/s [E31*S]
Vb = 7.8 m/s [E25*N]
Homework Equations
delta V = Vb - Va
delta V = Vb + (-Va)
The Attempt at a Solution
I am stuck between two solutions:
#1. Simply subtracting...
Homework Statement
In an anniversary celebration of Marilyn Bell's 1954 crossing of Lake Ontario a swimmer set out from the shores of New York and maintained a velocity of 4m/s [N]. As the swimmer approached the Ontario shore, she encountered a cross current of 2m/s [E 25deg S]. Find her...