maths: A person of unknown mass is going to jump off a diving board 4 meters high.

[richardhutton001]

Hi Guys,
My brain is a bit slow this morning and I need help Here${\displaystyle smyprob\le m.-Apersonofunknownmassisgo\in g\to ju\mp offa÷\in gboard4meter}$s high. The person jumps a further 0.7 meter`s in the air before diving off the board. At what speed does the person enter the water ?

 

[Ishuda]

Hi Guys,
My brain is a bit slow this morning and I need help Here${\displaystyle smyprob\le m.-Apersonofunknownmassisgo\in g\to ju\mp offa÷\in gboard4meter}$s high. The person jumps a further 0.7 meter`s in the air before diving off the board. At what speed does the person enter the water ?

First, it seems to me that the problem is in the wrong section. This involves a little more than just arithmetic and may, under some circumstances, require at least the concept of differentials.

What are your thoughts? What have you done so far? Please show us your work even if you feel that it is wrong so we may try to help you. You might also read
http://www.freemathhelp.com/forum/threads/78006-Read-Before-Posting


Hint: The distance equation is
$\displaystyle d(t) = d_0\, +\, v_o\, (t-t_0)\, +\, \frac{1}{2}\, a\, (t\, -\, t_0)^2$
where a is the acceleration. What if you take t₀=0 to be the time at the greatest distance from the water, that distance to be zero, i.e. d₀=0, and distances to be measured downward. Well for one thing, the initially velocity is zero, i.e. v₀=0. Also a is the gravity constant [if I'm doing rough estimate I just use 10 but you should probably use a closer value]. Now, since velocity is given by
$\displaystyle v(t) = v_o\, +\, a\, (t\, -\, t_0)$
you should have everything you need to solve the problem.