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Homework Help: Mech energy and perplexing waterslide

  1. Nov 7, 2004 #1
    hello, glad this site exisits.

    i got a test coming up on work, power, k and p energy, so forth . . .

    i got two test problems here that i can't figure out for the life of me.

    a) While running a person dissapates .6 j of mechanical energy per kg of body mass. if a 60 kg runner dissapates a power of 70 W during a race, how fast is the person running? Assume a running step is 1.5 m long.

    b) A child slides without friction from a height of h along a cuved waterslide. She is launched from a height of h/5 into the pool.
    it looks as though the angle is 45 degrees in the slide and i need to find the distance or the x value when she lands in the pool.

    if anyone can help me out here or if you need further info, drop a line. thanks a lot in advance . . .

    peace . . .
     
  2. jcsd
  3. Nov 7, 2004 #2
    Does a) say 'per kg of body mass per step', by any chance?
     
  4. Nov 8, 2004 #3
    yeah, sorry. it does say that, so add that to the problem. heh.
     
  5. Nov 8, 2004 #4
    So if a person dissipates 0.6 J per kg per step, how much total energy does a person weighing 60 kg dissipate per step? Then, how much total energy does the runner disipate per meter? How does this compare to 70 W? 70 W means 70 J are being dissipated each second - so, if a person dissipated 140 J per meter, that would mean it took a person two seconds to run a meter. You can get the speed from this.

    In part b) - does the slide level off at the botom or does it end at an angle?
     
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