# @elena

posted by on .

You helped me with this question earlier today, the answer you got was incorrect, i tried looking through your calculations but i cant find the mistake. the program wont let me see the right answer just tells the answer i put in was wrong. can you please look over it again thank you

Extreme-sports enthusiasts have been known to jump off the top of El Capitan, a sheer granite cliff of height 910m in Yosemite National Park. Assume a jumper runs horizontally off the top of El Capitan with speed 5.0m/s and enjoys a freefall until she is 150m above the valley floor, at which time she opens her parachute .

Q: how long is the jumper in freefall? ignore air resistance

• @elena - ,

Without air resistance, the horizontal velocity does not matter.
The free fall is over a vertical distance of 150-910=-760m
S=v0t-(1/2)gt² where v0=0
t=sqrt(-2S/g)
=sqrt(2*760/9.81)
=12.45 s.

• @elena - ,

h=H-H(o) =910-150 =760 m/s
h=g•t^2/2,
t=sqrt(2•h/g) = sqrt(2•760/9.8)=
=sqrt (155)=12.45 s.

• @elena - ,

thank you.