Physics (work)

[Binalicious]

A 45.6 kg diver steps off a diving board and drops straight down into the water. The water provides an average net force of resistance of 1408 N to the diver’s fall.
If the diver comes to rest 5 m below the water’s surface, what is the total distance be- tween the diving board and the diver’s stop- ping point underwater? The acceleration due to gravity is 9.81 m/s2 .
Answer in units of m

[factor-fiction]

I'll look back in a bit (just doing cooking)- will help later if needed.

[factor-fiction]

You will need to do in 2 stages I think

[vascop]

1. Use v^2=u^2+2fs to get an equation for v^2 of the diver when he/she hits the water. (you know u and f)
2. Calculate the deceleration when in the water, using F=ma (you know F and m)
3. Use v^2=u^2-2fs again (You know v^2, equation for u^2 and f and s).
4. Solve this for the unknown s in part 1 above (This is the distance of the diving board from the water
5. Add 5 to the result in 4 to give you the distance between the diving board and the point where the diver stops.

Have ago!

[argorstran]

Is there a considerably easier way of doing this by potential energy and work done by the water absorbing the potential energy ?
energy absorbed by water = P.E. of diver
force x distance = mass x acceleraion due to gravity x height
1408 x 5 = 45.6 x 9.81 x h
Maybe I've missed something (about 30yrs since I studied this ....)

[vascop]

Yes argor, I've done the calcs and your method and my method give the same answer, according to me.
Yours is a bit quicker and it looks as though that's the way they want you to do it, since the title says of the post has the word work in it.
Getting the same answer 2 different ways means there's a good chance we got it right!

[vascop]

Binalicious
Where areeeeeeeeeeeeeeee youuuuuuuuuuuuuuuuuuuuuuuuuuuuu?