time it takes the coin to fall: h=1/2 g t^2
t=sqrt(2h/g)
time it takes sound to come back: h/vs
given: those times add to 5.2 seconds
5.2=sqrt(2H/g)+h/v
a quadratic: let u=sqrt h so u^2=h
u^2/v+u(sqrt2/g)-5.2=0
u^2+u*vsqrt(2/g)-5.2v=0
calculate v for that temerature, then use the quadratic equation to solve for u (and square it for h)
The temperature of the air is 20 Celsius when a tourist drops a coin into a wishing well. She hears the splash 5.30s after she drops the coin. If the air resistance is ignored, how deep is the well?
a) 344m b)332m c)137m d)120m e)0.60m
2 answers
i dont really understand the explanation, so which would be the answer