physics problem

[peterhuang913]

Here a physics problem that came to my mind. If somebody thats just standing and he leaps into the air straight up and falls down to the same spot where he jumped, how high did he reach if the jumping and falling took .91 seconds?

 

[ncjimn]

so assuming i did this right, he reaches a height of 1.01442m.

That assuming no wind resistance, earth's gravity, and ignoring earth's rotation (if he jumps straight up, he'll land at a different spot since earth is rotating).

 

[peterhuang913]

how did you get to that answer?

 

[ncjimn]

is it right?

 

[peterhuang913]

its about 40 inches

 

[ncjimn]

40in * .0254m/in = 1.01600m ~=1.01442m

it was pretty easy. (using metric units) we know that g = 9.8m/s^2 and we know that the time going up is the same as the time going down. So I just integrated twice to get displacement over half of the .91 seconds.

it all comes down to this:

a = dv/dt = d^2x/dt^2,

where a = acceleration v = velocity x = displacement

 

[Nitestick]

seems right to me. peterhuang, why would you use anything but SI units for physics?

 

[Apokalipse]

It's also assuming his feet are always in exactly the same position relative to the rest of his body.

*edit*
Nitestick, update your signature! you are now in the folding@home 20k club!
I'm just a shave off 20k myself. I've prepared my sig image in advance.

 

[Nitestick]

yeah i noticed a few days ago but i've been too lazy to 'chop a new one

 

[Snake-Eyes]

peterhuang, why would you use anything but SI units for physics?

Homework lol.