# Homework Help: Mech energy and perplexing waterslide

1. Nov 7, 2004

### sanstereo

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. Nov 7, 2004

### Duarh

Does a) say 'per kg of body mass per step', by any chance?

3. Nov 8, 2004

### sanstereo

yeah, sorry. it does say that, so add that to the problem. heh.

4. Nov 8, 2004

### Duarh

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?