Recent content by yowatup

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?

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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...