Physics

[Draphoelix]

So I had this test in Physics and I thought it went all well. Until I asked my classmates about the last question where all seemed to have different answers. There's a number of questions but what's bugging is the last one where they are asking me about the velocity of Oscar when he jumps (I assume it's the beginning of the jump).

Here it is (roughly translated)

Oscar is standing on a scale. He jumps. There's a gauge that measures the time and how much newton/force is affecting the scale (during this time).
There's also a diagram that shows that during the first seconds, the amount of force is around 720 N. After that, during 0,5 seconds, the amount of force = 0. Then there's a peak point for a split-second that's around 2000 N.

Which means that Oscar weighs around 720/9.82 kg. When he jumps he's in the air for 0,5 seconds and when he lands he's affecting the scale with around 2000 N (I think).

So what I did was calculating the distance by using

s = v[SUB]0[/SUB]t + (at^2/2)

(where t = 0,25, half of the total time)

Then through the law of Mechanical Energy, the answer I've got was 2,46 m/s. But there were alot of people that got around 4-5 seconds. I didn't take the 2000 N when he lands into account at all. Should I?